diff --git a/pgio/README.md b/pgio/README.md
new file mode 100644
index 00000000..b2fc5801
--- /dev/null
+++ b/pgio/README.md
@@ -0,0 +1,6 @@
+# pgio
+
+Package pgio is a low-level toolkit building messages in the PostgreSQL wire protocol.
+
+pgio provides functions for appending integers to a []byte while doing byte
+order conversion.
diff --git a/pgio/doc.go b/pgio/doc.go
new file mode 100644
index 00000000..ef2dcc7f
--- /dev/null
+++ b/pgio/doc.go
@@ -0,0 +1,6 @@
+// Package pgio is a low-level toolkit building messages in the PostgreSQL wire protocol.
+/*
+pgio provides functions for appending integers to a []byte while doing byte
+order conversion.
+*/
+package pgio
diff --git a/pgio/write.go b/pgio/write.go
new file mode 100644
index 00000000..96aedf9d
--- /dev/null
+++ b/pgio/write.go
@@ -0,0 +1,40 @@
+package pgio
+
+import "encoding/binary"
+
+func AppendUint16(buf []byte, n uint16) []byte {
+	wp := len(buf)
+	buf = append(buf, 0, 0)
+	binary.BigEndian.PutUint16(buf[wp:], n)
+	return buf
+}
+
+func AppendUint32(buf []byte, n uint32) []byte {
+	wp := len(buf)
+	buf = append(buf, 0, 0, 0, 0)
+	binary.BigEndian.PutUint32(buf[wp:], n)
+	return buf
+}
+
+func AppendUint64(buf []byte, n uint64) []byte {
+	wp := len(buf)
+	buf = append(buf, 0, 0, 0, 0, 0, 0, 0, 0)
+	binary.BigEndian.PutUint64(buf[wp:], n)
+	return buf
+}
+
+func AppendInt16(buf []byte, n int16) []byte {
+	return AppendUint16(buf, uint16(n))
+}
+
+func AppendInt32(buf []byte, n int32) []byte {
+	return AppendUint32(buf, uint32(n))
+}
+
+func AppendInt64(buf []byte, n int64) []byte {
+	return AppendUint64(buf, uint64(n))
+}
+
+func SetInt32(buf []byte, n int32) {
+	binary.BigEndian.PutUint32(buf, uint32(n))
+}
diff --git a/pgio/write_test.go b/pgio/write_test.go
new file mode 100644
index 00000000..bd50e71c
--- /dev/null
+++ b/pgio/write_test.go
@@ -0,0 +1,78 @@
+package pgio
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestAppendUint16NilBuf(t *testing.T) {
+	buf := AppendUint16(nil, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 1}) {
+		t.Errorf("AppendUint16(nil, 1) => %v, want %v", buf, []byte{0, 1})
+	}
+}
+
+func TestAppendUint16EmptyBuf(t *testing.T) {
+	buf := []byte{}
+	buf = AppendUint16(buf, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 1}) {
+		t.Errorf("AppendUint16(nil, 1) => %v, want %v", buf, []byte{0, 1})
+	}
+}
+
+func TestAppendUint16BufWithCapacityDoesNotAllocate(t *testing.T) {
+	buf := make([]byte, 0, 4)
+	AppendUint16(buf, 1)
+	buf = buf[0:2]
+	if !reflect.DeepEqual(buf, []byte{0, 1}) {
+		t.Errorf("AppendUint16(nil, 1) => %v, want %v", buf, []byte{0, 1})
+	}
+}
+
+func TestAppendUint32NilBuf(t *testing.T) {
+	buf := AppendUint32(nil, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 1}) {
+		t.Errorf("AppendUint32(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 1})
+	}
+}
+
+func TestAppendUint32EmptyBuf(t *testing.T) {
+	buf := []byte{}
+	buf = AppendUint32(buf, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 1}) {
+		t.Errorf("AppendUint32(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 1})
+	}
+}
+
+func TestAppendUint32BufWithCapacityDoesNotAllocate(t *testing.T) {
+	buf := make([]byte, 0, 4)
+	AppendUint32(buf, 1)
+	buf = buf[0:4]
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 1}) {
+		t.Errorf("AppendUint32(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 1})
+	}
+}
+
+func TestAppendUint64NilBuf(t *testing.T) {
+	buf := AppendUint64(nil, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 0, 0, 0, 0, 1}) {
+		t.Errorf("AppendUint64(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 0, 0, 0, 0, 1})
+	}
+}
+
+func TestAppendUint64EmptyBuf(t *testing.T) {
+	buf := []byte{}
+	buf = AppendUint64(buf, 1)
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 0, 0, 0, 0, 1}) {
+		t.Errorf("AppendUint64(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 0, 0, 0, 0, 1})
+	}
+}
+
+func TestAppendUint64BufWithCapacityDoesNotAllocate(t *testing.T) {
+	buf := make([]byte, 0, 8)
+	AppendUint64(buf, 1)
+	buf = buf[0:8]
+	if !reflect.DeepEqual(buf, []byte{0, 0, 0, 0, 0, 0, 0, 1}) {
+		t.Errorf("AppendUint64(nil, 1) => %v, want %v", buf, []byte{0, 0, 0, 0, 0, 0, 0, 1})
+	}
+}