diff --git a/authentication.go b/authentication.go
index 54f4978f..c04ee448 100644
--- a/authentication.go
+++ b/authentication.go
@@ -1,9 +1,10 @@
 package pgproto3
 
 import (
-	"bytes"
 	"encoding/binary"
 	"fmt"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 const (
@@ -36,19 +37,18 @@ func (dst *Authentication) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Authentication) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-	buf.WriteByte('R')
-	buf.Write(bigEndian.Uint32(0))
-	buf.Write(bigEndian.Uint32(src.Type))
+func (src *Authentication) Encode(dst []byte) []byte {
+	dst = append(dst, 'R')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
+	dst = pgio.AppendUint32(dst, src.Type)
 
 	switch src.Type {
 	case AuthTypeMD5Password:
-		buf.Write(src.Salt[:])
+		dst = append(dst, src.Salt[:]...)
 	}
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
diff --git a/backend.go b/backend.go
index df66a799..bf96ba95 100644
--- a/backend.go
+++ b/backend.go
@@ -32,12 +32,7 @@ func NewBackend(r io.Reader, w io.Writer) (*Backend, error) {
 }
 
 func (b *Backend) Send(msg BackendMessage) error {
-	buf, err := msg.MarshalBinary()
-	if err != nil {
-		return nil
-	}
-
-	_, err = b.w.Write(buf)
+	_, err := b.w.Write(msg.Encode(nil))
 	return err
 }
 
diff --git a/backend_key_data.go b/backend_key_data.go
index 04f31aec..5a478f10 100644
--- a/backend_key_data.go
+++ b/backend_key_data.go
@@ -1,9 +1,10 @@
 package pgproto3
 
 import (
-	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type BackendKeyData struct {
@@ -24,14 +25,12 @@ func (dst *BackendKeyData) Decode(src []byte) error {
 	return nil
 }
 
-func (src *BackendKeyData) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-	buf.WriteByte('K')
-	buf.Write(bigEndian.Uint32(12))
-	buf.Write(bigEndian.Uint32(src.ProcessID))
-	buf.Write(bigEndian.Uint32(src.SecretKey))
-	return buf.Bytes(), nil
+func (src *BackendKeyData) Encode(dst []byte) []byte {
+	dst = append(dst, 'K')
+	dst = pgio.AppendUint32(dst, 12)
+	dst = pgio.AppendUint32(dst, src.ProcessID)
+	dst = pgio.AppendUint32(dst, src.SecretKey)
+	return dst
 }
 
 func (src *BackendKeyData) MarshalJSON() ([]byte, error) {
diff --git a/bind.go b/bind.go
index 79fb4503..cceee6ab 100644
--- a/bind.go
+++ b/bind.go
@@ -5,6 +5,8 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Bind struct {
@@ -101,45 +103,40 @@ func (dst *Bind) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Bind) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *Bind) Encode(dst []byte) []byte {
+	dst = append(dst, 'B')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('B')
-	buf.Write(bigEndian.Uint32(0))
-
-	buf.WriteString(src.DestinationPortal)
-	buf.WriteByte(0)
-	buf.WriteString(src.PreparedStatement)
-	buf.WriteByte(0)
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ParameterFormatCodes))))
+	dst = append(dst, src.DestinationPortal...)
+	dst = append(dst, 0)
+	dst = append(dst, src.PreparedStatement...)
+	dst = append(dst, 0)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.ParameterFormatCodes)))
 	for _, fc := range src.ParameterFormatCodes {
-		buf.Write(bigEndian.Int16(fc))
+		dst = pgio.AppendInt16(dst, fc)
 	}
 
-	buf.Write(bigEndian.Uint16(uint16(len(src.Parameters))))
-
+	dst = pgio.AppendUint16(dst, uint16(len(src.Parameters)))
 	for _, p := range src.Parameters {
 		if p == nil {
-			buf.Write(bigEndian.Int32(-1))
+			dst = pgio.AppendInt32(dst, -1)
 			continue
 		}
 
-		buf.Write(bigEndian.Int32(int32(len(p))))
-		buf.Write(p)
+		dst = pgio.AppendInt32(dst, int32(len(p)))
+		dst = append(dst, p...)
 	}
 
-	buf.Write(bigEndian.Uint16(uint16(len(src.ResultFormatCodes))))
-
+	dst = pgio.AppendUint16(dst, uint16(len(src.ResultFormatCodes)))
 	for _, fc := range src.ResultFormatCodes {
-		buf.Write(bigEndian.Int16(fc))
+		dst = pgio.AppendInt16(dst, fc)
 	}
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *Bind) MarshalJSON() ([]byte, error) {
diff --git a/bind_complete.go b/bind_complete.go
index 4f1c44b8..60360519 100644
--- a/bind_complete.go
+++ b/bind_complete.go
@@ -16,8 +16,8 @@ func (dst *BindComplete) Decode(src []byte) error {
 	return nil
 }
 
-func (src *BindComplete) MarshalBinary() ([]byte, error) {
-	return []byte{'2', 0, 0, 0, 4}, nil
+func (src *BindComplete) Encode(dst []byte) []byte {
+	return append(dst, '2', 0, 0, 0, 4)
 }
 
 func (src *BindComplete) MarshalJSON() ([]byte, error) {
diff --git a/close.go b/close.go
index 454ef68e..5ff4c886 100644
--- a/close.go
+++ b/close.go
@@ -2,8 +2,9 @@ package pgproto3
 
 import (
 	"bytes"
-	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Close struct {
@@ -31,20 +32,18 @@ func (dst *Close) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Close) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *Close) Encode(dst []byte) []byte {
+	dst = append(dst, 'C')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('C')
-	buf.Write(bigEndian.Uint32(0))
+	dst = append(dst, src.ObjectType)
+	dst = append(dst, src.Name...)
+	dst = append(dst, 0)
 
-	buf.WriteByte(src.ObjectType)
-	buf.WriteString(src.Name)
-	buf.WriteByte(0)
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
-
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *Close) MarshalJSON() ([]byte, error) {
diff --git a/close_complete.go b/close_complete.go
index 9bab3e8c..db793c94 100644
--- a/close_complete.go
+++ b/close_complete.go
@@ -16,8 +16,8 @@ func (dst *CloseComplete) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CloseComplete) MarshalBinary() ([]byte, error) {
-	return []byte{'3', 0, 0, 0, 4}, nil
+func (src *CloseComplete) Encode(dst []byte) []byte {
+	return append(dst, '3', 0, 0, 0, 4)
 }
 
 func (src *CloseComplete) MarshalJSON() ([]byte, error) {
diff --git a/command_complete.go b/command_complete.go
index 86653804..85848532 100644
--- a/command_complete.go
+++ b/command_complete.go
@@ -3,6 +3,8 @@ package pgproto3
 import (
 	"bytes"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type CommandComplete struct {
@@ -22,17 +24,17 @@ func (dst *CommandComplete) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CommandComplete) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *CommandComplete) Encode(dst []byte) []byte {
+	dst = append(dst, 'C')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('C')
-	buf.Write(bigEndian.Uint32(uint32(4 + len(src.CommandTag) + 1)))
+	dst = append(dst, src.CommandTag...)
+	dst = append(dst, 0)
 
-	buf.WriteString(src.CommandTag)
-	buf.WriteByte(0)
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *CommandComplete) MarshalJSON() ([]byte, error) {
diff --git a/copy_both_response.go b/copy_both_response.go
index 3857c187..2862a34f 100644
--- a/copy_both_response.go
+++ b/copy_both_response.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type CopyBothResponse struct {
@@ -37,20 +39,19 @@ func (dst *CopyBothResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CopyBothResponse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('W')
-	buf.Write(bigEndian.Uint32(uint32(4 + 1 + 2 + 2*len(src.ColumnFormatCodes))))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ColumnFormatCodes))))
+func (src *CopyBothResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'W')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.ColumnFormatCodes)))
 	for _, fc := range src.ColumnFormatCodes {
-		buf.Write(bigEndian.Uint16(fc))
+		dst = pgio.AppendUint16(dst, fc)
 	}
 
-	return buf.Bytes(), nil
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
 }
 
 func (src *CopyBothResponse) MarshalJSON() ([]byte, error) {
diff --git a/copy_data.go b/copy_data.go
index de7ab4ff..fab139e6 100644
--- a/copy_data.go
+++ b/copy_data.go
@@ -1,9 +1,10 @@
 package pgproto3
 
 import (
-	"bytes"
 	"encoding/hex"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type CopyData struct {
@@ -18,15 +19,11 @@ func (dst *CopyData) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CopyData) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('d')
-	buf.Write(bigEndian.Uint32(uint32(4 + len(src.Data))))
-	buf.Write(src.Data)
-
-	return buf.Bytes(), nil
+func (src *CopyData) Encode(dst []byte) []byte {
+	dst = append(dst, 'd')
+	dst = pgio.AppendInt32(dst, int32(4+len(src.Data)))
+	dst = append(dst, src.Data...)
+	return dst
 }
 
 func (src *CopyData) MarshalJSON() ([]byte, error) {
diff --git a/copy_in_response.go b/copy_in_response.go
index 9854d665..54083cd6 100644
--- a/copy_in_response.go
+++ b/copy_in_response.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type CopyInResponse struct {
@@ -37,20 +39,19 @@ func (dst *CopyInResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CopyInResponse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('G')
-	buf.Write(bigEndian.Uint32(uint32(4 + 1 + 2 + 2*len(src.ColumnFormatCodes))))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ColumnFormatCodes))))
+func (src *CopyInResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'G')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.ColumnFormatCodes)))
 	for _, fc := range src.ColumnFormatCodes {
-		buf.Write(bigEndian.Uint16(fc))
+		dst = pgio.AppendUint16(dst, fc)
 	}
 
-	return buf.Bytes(), nil
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
 }
 
 func (src *CopyInResponse) MarshalJSON() ([]byte, error) {
diff --git a/copy_out_response.go b/copy_out_response.go
index 5ef6e4c1..eaa33b8b 100644
--- a/copy_out_response.go
+++ b/copy_out_response.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type CopyOutResponse struct {
@@ -37,20 +39,19 @@ func (dst *CopyOutResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *CopyOutResponse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('H')
-	buf.Write(bigEndian.Uint32(uint32(4 + 1 + 2 + 2*len(src.ColumnFormatCodes))))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ColumnFormatCodes))))
+func (src *CopyOutResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'H')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.ColumnFormatCodes)))
 	for _, fc := range src.ColumnFormatCodes {
-		buf.Write(bigEndian.Uint16(fc))
+		dst = pgio.AppendUint16(dst, fc)
 	}
 
-	return buf.Bytes(), nil
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
 }
 
 func (src *CopyOutResponse) MarshalJSON() ([]byte, error) {
diff --git a/data_row.go b/data_row.go
index 3e600e84..e46d3cc0 100644
--- a/data_row.go
+++ b/data_row.go
@@ -1,10 +1,11 @@
 package pgproto3
 
 import (
-	"bytes"
 	"encoding/binary"
 	"encoding/hex"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type DataRow struct {
@@ -58,28 +59,25 @@ func (dst *DataRow) Decode(src []byte) error {
 	return nil
 }
 
-func (src *DataRow) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('D')
-	buf.Write(bigEndian.Uint32(0))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.Values))))
+func (src *DataRow) Encode(dst []byte) []byte {
+	dst = append(dst, 'D')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.Values)))
 	for _, v := range src.Values {
 		if v == nil {
-			buf.Write(bigEndian.Int32(-1))
+			dst = pgio.AppendInt32(dst, -1)
 			continue
 		}
 
-		buf.Write(bigEndian.Int32(int32(len(v))))
-		buf.Write(v)
+		dst = pgio.AppendInt32(dst, int32(len(v)))
+		dst = append(dst, v...)
 	}
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *DataRow) MarshalJSON() ([]byte, error) {
diff --git a/describe.go b/describe.go
index ea55ed9d..bb7bc056 100644
--- a/describe.go
+++ b/describe.go
@@ -2,8 +2,9 @@ package pgproto3
 
 import (
 	"bytes"
-	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Describe struct {
@@ -31,20 +32,18 @@ func (dst *Describe) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Describe) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *Describe) Encode(dst []byte) []byte {
+	dst = append(dst, 'D')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('D')
-	buf.Write(bigEndian.Uint32(0))
+	dst = append(dst, src.ObjectType)
+	dst = append(dst, src.Name...)
+	dst = append(dst, 0)
 
-	buf.WriteByte(src.ObjectType)
-	buf.WriteString(src.Name)
-	buf.WriteByte(0)
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
-
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *Describe) MarshalJSON() ([]byte, error) {
diff --git a/empty_query_response.go b/empty_query_response.go
index 13ed1886..d283b06d 100644
--- a/empty_query_response.go
+++ b/empty_query_response.go
@@ -16,8 +16,8 @@ func (dst *EmptyQueryResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *EmptyQueryResponse) MarshalBinary() ([]byte, error) {
-	return []byte{'I', 0, 0, 0, 4}, nil
+func (src *EmptyQueryResponse) Encode(dst []byte) []byte {
+	return append(dst, 'I', 0, 0, 0, 4)
 }
 
 func (src *EmptyQueryResponse) MarshalJSON() ([]byte, error) {
diff --git a/error_response.go b/error_response.go
index 602dd2a1..160234f2 100644
--- a/error_response.go
+++ b/error_response.go
@@ -103,11 +103,11 @@ func (dst *ErrorResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *ErrorResponse) MarshalBinary() ([]byte, error) {
-	return src.marshalBinary('E')
+func (src *ErrorResponse) Encode(dst []byte) []byte {
+	return append(dst, src.marshalBinary('E')...)
 }
 
-func (src *ErrorResponse) marshalBinary(typeByte byte) ([]byte, error) {
+func (src *ErrorResponse) marshalBinary(typeByte byte) []byte {
 	var bigEndian BigEndianBuf
 	buf := &bytes.Buffer{}
 
@@ -193,5 +193,5 @@ func (src *ErrorResponse) marshalBinary(typeByte byte) ([]byte, error) {
 
 	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
 
-	return buf.Bytes(), nil
+	return buf.Bytes()
 }
diff --git a/execute.go b/execute.go
index 4892e7b3..76da9943 100644
--- a/execute.go
+++ b/execute.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Execute struct {
@@ -30,21 +32,19 @@ func (dst *Execute) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Execute) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *Execute) Encode(dst []byte) []byte {
+	dst = append(dst, 'E')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('E')
-	buf.Write(bigEndian.Uint32(0))
+	dst = append(dst, src.Portal...)
+	dst = append(dst, 0)
 
-	buf.WriteString(src.Portal)
-	buf.WriteByte(0)
+	dst = pgio.AppendUint32(dst, src.MaxRows)
 
-	buf.Write(bigEndian.Uint32(src.MaxRows))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
-
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *Execute) MarshalJSON() ([]byte, error) {
diff --git a/flush.go b/flush.go
index d26f5c0c..7fd5e987 100644
--- a/flush.go
+++ b/flush.go
@@ -16,8 +16,8 @@ func (dst *Flush) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Flush) MarshalBinary() ([]byte, error) {
-	return []byte{'H', 0, 0, 0, 4}, nil
+func (src *Flush) Encode(dst []byte) []byte {
+	return append(dst, 'H', 0, 0, 0, 4)
 }
 
 func (src *Flush) MarshalJSON() ([]byte, error) {
diff --git a/frontend.go b/frontend.go
index 27a9890a..630a5cba 100644
--- a/frontend.go
+++ b/frontend.go
@@ -42,12 +42,7 @@ func NewFrontend(r io.Reader, w io.Writer) (*Frontend, error) {
 }
 
 func (b *Frontend) Send(msg FrontendMessage) error {
-	buf, err := msg.MarshalBinary()
-	if err != nil {
-		return nil
-	}
-
-	_, err = b.w.Write(buf)
+	_, err := b.w.Write(msg.Encode(nil))
 	return err
 }
 
diff --git a/function_call_response.go b/function_call_response.go
index 1e0f16af..bb325b69 100644
--- a/function_call_response.go
+++ b/function_call_response.go
@@ -1,10 +1,11 @@
 package pgproto3
 
 import (
-	"bytes"
 	"encoding/binary"
 	"encoding/hex"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type FunctionCallResponse struct {
@@ -34,21 +35,21 @@ func (dst *FunctionCallResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *FunctionCallResponse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('V')
-	buf.Write(bigEndian.Uint32(uint32(4 + 4 + len(src.Result))))
+func (src *FunctionCallResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'V')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
 	if src.Result == nil {
-		buf.Write(bigEndian.Int32(-1))
+		dst = pgio.AppendInt32(dst, -1)
 	} else {
-		buf.Write(bigEndian.Int32(int32(len(src.Result))))
-		buf.Write(src.Result)
+		dst = pgio.AppendInt32(dst, int32(len(src.Result)))
+		dst = append(dst, src.Result...)
 	}
 
-	return buf.Bytes(), nil
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
 }
 
 func (src *FunctionCallResponse) MarshalJSON() ([]byte, error) {
diff --git a/no_data.go b/no_data.go
index 3adec4ad..1fb47c2a 100644
--- a/no_data.go
+++ b/no_data.go
@@ -16,8 +16,8 @@ func (dst *NoData) Decode(src []byte) error {
 	return nil
 }
 
-func (src *NoData) MarshalBinary() ([]byte, error) {
-	return []byte{'n', 0, 0, 0, 4}, nil
+func (src *NoData) Encode(dst []byte) []byte {
+	return append(dst, 'n', 0, 0, 0, 4)
 }
 
 func (src *NoData) MarshalJSON() ([]byte, error) {
diff --git a/notice_response.go b/notice_response.go
index 8af55baf..e4595aa5 100644
--- a/notice_response.go
+++ b/notice_response.go
@@ -8,6 +8,6 @@ func (dst *NoticeResponse) Decode(src []byte) error {
 	return (*ErrorResponse)(dst).Decode(src)
 }
 
-func (src *NoticeResponse) MarshalBinary() ([]byte, error) {
-	return (*ErrorResponse)(src).marshalBinary('N')
+func (src *NoticeResponse) Encode(dst []byte) []byte {
+	return append(dst, (*ErrorResponse)(src).marshalBinary('N')...)
 }
diff --git a/notification_response.go b/notification_response.go
index 7262844e..b14007b4 100644
--- a/notification_response.go
+++ b/notification_response.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type NotificationResponse struct {
@@ -35,19 +37,19 @@ func (dst *NotificationResponse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *NotificationResponse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *NotificationResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'A')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('A')
-	buf.Write(bigEndian.Uint32(uint32(4 + 4 + len(src.Channel) + len(src.Payload))))
+	dst = append(dst, src.Channel...)
+	dst = append(dst, 0)
+	dst = append(dst, src.Payload...)
+	dst = append(dst, 0)
 
-	buf.WriteString(src.Channel)
-	buf.WriteByte(0)
-	buf.WriteString(src.Payload)
-	buf.WriteByte(0)
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *NotificationResponse) MarshalJSON() ([]byte, error) {
diff --git a/parameter_description.go b/parameter_description.go
index 32b6e1c1..1fa3c927 100644
--- a/parameter_description.go
+++ b/parameter_description.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type ParameterDescription struct {
@@ -33,20 +35,19 @@ func (dst *ParameterDescription) Decode(src []byte) error {
 	return nil
 }
 
-func (src *ParameterDescription) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('t')
-	buf.Write(bigEndian.Uint32(uint32(4 + 2 + 4*len(src.ParameterOIDs))))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ParameterOIDs))))
+func (src *ParameterDescription) Encode(dst []byte) []byte {
+	dst = append(dst, 't')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.ParameterOIDs)))
 	for _, oid := range src.ParameterOIDs {
-		buf.Write(bigEndian.Uint32(oid))
+		dst = pgio.AppendUint32(dst, oid)
 	}
 
-	return buf.Bytes(), nil
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
 }
 
 func (src *ParameterDescription) MarshalJSON() ([]byte, error) {
diff --git a/parameter_status.go b/parameter_status.go
index 9b10824c..b3bac33f 100644
--- a/parameter_status.go
+++ b/parameter_status.go
@@ -2,8 +2,9 @@ package pgproto3
 
 import (
 	"bytes"
-	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type ParameterStatus struct {
@@ -32,21 +33,19 @@ func (dst *ParameterStatus) Decode(src []byte) error {
 	return nil
 }
 
-func (src *ParameterStatus) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *ParameterStatus) Encode(dst []byte) []byte {
+	dst = append(dst, 'S')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('S')
-	buf.Write(bigEndian.Uint32(0))
+	dst = append(dst, src.Name...)
+	dst = append(dst, 0)
+	dst = append(dst, src.Value...)
+	dst = append(dst, 0)
 
-	buf.WriteString(src.Name)
-	buf.WriteByte(0)
-	buf.WriteString(src.Value)
-	buf.WriteByte(0)
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
-
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (ps *ParameterStatus) MarshalJSON() ([]byte, error) {
diff --git a/parse.go b/parse.go
index 5d17ed11..b8775547 100644
--- a/parse.go
+++ b/parse.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Parse struct {
@@ -44,27 +46,24 @@ func (dst *Parse) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Parse) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
+func (src *Parse) Encode(dst []byte) []byte {
+	dst = append(dst, 'P')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
-	buf.WriteByte('P')
-	buf.Write(bigEndian.Uint32(0))
+	dst = append(dst, src.Name...)
+	dst = append(dst, 0)
+	dst = append(dst, src.Query...)
+	dst = append(dst, 0)
 
-	buf.WriteString(src.Name)
-	buf.WriteByte(0)
-	buf.WriteString(src.Query)
-	buf.WriteByte(0)
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.ParameterOIDs))))
-
-	for _, v := range src.ParameterOIDs {
-		buf.Write(bigEndian.Uint32(v))
+	dst = pgio.AppendUint16(dst, uint16(len(src.ParameterOIDs)))
+	for _, oid := range src.ParameterOIDs {
+		dst = pgio.AppendUint32(dst, oid)
 	}
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *Parse) MarshalJSON() ([]byte, error) {
diff --git a/parse_complete.go b/parse_complete.go
index e949c14c..462a89ba 100644
--- a/parse_complete.go
+++ b/parse_complete.go
@@ -16,8 +16,8 @@ func (dst *ParseComplete) Decode(src []byte) error {
 	return nil
 }
 
-func (src *ParseComplete) MarshalBinary() ([]byte, error) {
-	return []byte{'1', 0, 0, 0, 4}, nil
+func (src *ParseComplete) Encode(dst []byte) []byte {
+	return append(dst, '1', 0, 0, 0, 4)
 }
 
 func (src *ParseComplete) MarshalJSON() ([]byte, error) {
diff --git a/password_message.go b/password_message.go
index 69df6362..2ad3fe4a 100644
--- a/password_message.go
+++ b/password_message.go
@@ -3,6 +3,8 @@ package pgproto3
 import (
 	"bytes"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type PasswordMessage struct {
@@ -23,14 +25,14 @@ func (dst *PasswordMessage) Decode(src []byte) error {
 	return nil
 }
 
-func (src *PasswordMessage) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-	buf.WriteByte('p')
-	buf.Write(bigEndian.Uint32(uint32(4 + len(src.Password) + 1)))
-	buf.WriteString(src.Password)
-	buf.WriteByte(0)
-	return buf.Bytes(), nil
+func (src *PasswordMessage) Encode(dst []byte) []byte {
+	dst = append(dst, 'p')
+	dst = pgio.AppendInt32(dst, int32(4+len(src.Password)+1))
+
+	dst = append(dst, src.Password...)
+	dst = append(dst, 0)
+
+	return dst
 }
 
 func (src *PasswordMessage) MarshalJSON() ([]byte, error) {
diff --git a/pgproto3.go b/pgproto3.go
index 3fe8fc93..fe7b085b 100644
--- a/pgproto3.go
+++ b/pgproto3.go
@@ -4,12 +4,13 @@ import "fmt"
 
 // Message is the interface implemented by an object that can decode and encode
 // a particular PostgreSQL message.
-//
-// Decode is allowed and expected to retain a reference to data after
-// returning (unlike encoding.BinaryUnmarshaler).
 type Message interface {
+	// Decode is allowed and expected to retain a reference to data after
+	// returning (unlike encoding.BinaryUnmarshaler).
 	Decode(data []byte) error
-	MarshalBinary() (data []byte, err error)
+
+	// Encode appends itself to dst and returns the new buffer.
+	Encode(dst []byte) []byte
 }
 
 type FrontendMessage interface {
diff --git a/query.go b/query.go
index b5fc2dbc..d80c0fb4 100644
--- a/query.go
+++ b/query.go
@@ -3,6 +3,8 @@ package pgproto3
 import (
 	"bytes"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 type Query struct {
@@ -22,14 +24,14 @@ func (dst *Query) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Query) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-	buf.WriteByte('Q')
-	buf.Write(bigEndian.Uint32(uint32(4 + len(src.String) + 1)))
-	buf.WriteString(src.String)
-	buf.WriteByte(0)
-	return buf.Bytes(), nil
+func (src *Query) Encode(dst []byte) []byte {
+	dst = append(dst, 'Q')
+	dst = pgio.AppendInt32(dst, int32(4+len(src.String)+1))
+
+	dst = append(dst, src.String...)
+	dst = append(dst, 0)
+
+	return dst
 }
 
 func (src *Query) MarshalJSON() ([]byte, error) {
diff --git a/ready_for_query.go b/ready_for_query.go
index e0e4707a..63b902bd 100644
--- a/ready_for_query.go
+++ b/ready_for_query.go
@@ -20,8 +20,8 @@ func (dst *ReadyForQuery) Decode(src []byte) error {
 	return nil
 }
 
-func (src *ReadyForQuery) MarshalBinary() ([]byte, error) {
-	return []byte{'Z', 0, 0, 0, 5, src.TxStatus}, nil
+func (src *ReadyForQuery) Encode(dst []byte) []byte {
+	return append(dst, 'Z', 0, 0, 0, 5, src.TxStatus)
 }
 
 func (src *ReadyForQuery) MarshalJSON() ([]byte, error) {
diff --git a/row_description.go b/row_description.go
index b1110290..d0df11b0 100644
--- a/row_description.go
+++ b/row_description.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 const (
@@ -64,30 +66,27 @@ func (dst *RowDescription) Decode(src []byte) error {
 	return nil
 }
 
-func (src *RowDescription) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-
-	buf.WriteByte('T')
-	buf.Write(bigEndian.Uint32(0))
-
-	buf.Write(bigEndian.Uint16(uint16(len(src.Fields))))
+func (src *RowDescription) Encode(dst []byte) []byte {
+	dst = append(dst, 'T')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
 
+	dst = pgio.AppendUint16(dst, uint16(len(src.Fields)))
 	for _, fd := range src.Fields {
-		buf.WriteString(fd.Name)
-		buf.WriteByte(0)
+		dst = append(dst, fd.Name...)
+		dst = append(dst, 0)
 
-		buf.Write(bigEndian.Uint32(fd.TableOID))
-		buf.Write(bigEndian.Uint16(fd.TableAttributeNumber))
-		buf.Write(bigEndian.Uint32(fd.DataTypeOID))
-		buf.Write(bigEndian.Uint16(uint16(fd.DataTypeSize)))
-		buf.Write(bigEndian.Uint32(fd.TypeModifier))
-		buf.Write(bigEndian.Uint16(uint16(fd.Format)))
+		dst = pgio.AppendUint32(dst, fd.TableOID)
+		dst = pgio.AppendUint16(dst, fd.TableAttributeNumber)
+		dst = pgio.AppendUint32(dst, fd.DataTypeOID)
+		dst = pgio.AppendInt16(dst, fd.DataTypeSize)
+		dst = pgio.AppendUint32(dst, fd.TypeModifier)
+		dst = pgio.AppendInt16(dst, fd.Format)
 	}
 
-	binary.BigEndian.PutUint32(buf.Bytes()[1:5], uint32(buf.Len()-1))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *RowDescription) MarshalJSON() ([]byte, error) {
diff --git a/startup_message.go b/startup_message.go
index 4847d629..4e2df27d 100644
--- a/startup_message.go
+++ b/startup_message.go
@@ -5,6 +5,8 @@ import (
 	"encoding/binary"
 	"encoding/json"
 	"fmt"
+
+	"github.com/jackc/pgx/pgio"
 )
 
 const (
@@ -64,22 +66,22 @@ func (dst *StartupMessage) Decode(src []byte) error {
 	return nil
 }
 
-func (src *StartupMessage) MarshalBinary() ([]byte, error) {
-	var bigEndian BigEndianBuf
-	buf := &bytes.Buffer{}
-	buf.Write(bigEndian.Uint32(0))
-	buf.Write(bigEndian.Uint32(src.ProtocolVersion))
+func (src *StartupMessage) Encode(dst []byte) []byte {
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
+
+	dst = pgio.AppendUint32(dst, src.ProtocolVersion)
 	for k, v := range src.Parameters {
-		buf.WriteString(k)
-		buf.WriteByte(0)
-		buf.WriteString(v)
-		buf.WriteByte(0)
+		dst = append(dst, k...)
+		dst = append(dst, 0)
+		dst = append(dst, v...)
+		dst = append(dst, 0)
 	}
-	buf.WriteByte(0)
+	dst = append(dst, 0)
 
-	binary.BigEndian.PutUint32(buf.Bytes()[0:4], uint32(buf.Len()))
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 
-	return buf.Bytes(), nil
+	return dst
 }
 
 func (src *StartupMessage) MarshalJSON() ([]byte, error) {
diff --git a/sync.go b/sync.go
index da3fa727..85f4749a 100644
--- a/sync.go
+++ b/sync.go
@@ -16,8 +16,8 @@ func (dst *Sync) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Sync) MarshalBinary() ([]byte, error) {
-	return []byte{'S', 0, 0, 0, 4}, nil
+func (src *Sync) Encode(dst []byte) []byte {
+	return append(dst, 'S', 0, 0, 0, 4)
 }
 
 func (src *Sync) MarshalJSON() ([]byte, error) {
diff --git a/terminate.go b/terminate.go
index 77977f20..0a3310da 100644
--- a/terminate.go
+++ b/terminate.go
@@ -16,8 +16,8 @@ func (dst *Terminate) Decode(src []byte) error {
 	return nil
 }
 
-func (src *Terminate) MarshalBinary() ([]byte, error) {
-	return []byte{'X', 0, 0, 0, 4}, nil
+func (src *Terminate) Encode(dst []byte) []byte {
+	return append(dst, 'X', 0, 0, 0, 4)
 }
 
 func (src *Terminate) MarshalJSON() ([]byte, error) {