diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 1f893951c15..54029cd40fd 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"os"
 	"strings"
 	"testing"
 	"testing/iotest"
@@ -425,9 +424,9 @@ var errorWriterTests = []errorWriterTest{
 	{0, 1, nil, io.ErrShortWrite},
 	{1, 2, nil, io.ErrShortWrite},
 	{1, 1, nil, nil},
-	{0, 1, os.EPIPE, os.EPIPE},
-	{1, 2, os.EPIPE, os.EPIPE},
-	{1, 1, os.EPIPE, os.EPIPE},
+	{0, 1, io.ErrClosedPipe, io.ErrClosedPipe},
+	{1, 2, io.ErrClosedPipe, io.ErrClosedPipe},
+	{1, 1, io.ErrClosedPipe, io.ErrClosedPipe},
 }
 
 func TestWriteErrors(t *testing.T) {
diff --git a/src/pkg/compress/lzw/reader.go b/src/pkg/compress/lzw/reader.go
index c787a9568b3..0ed742c8977 100644
--- a/src/pkg/compress/lzw/reader.go
+++ b/src/pkg/compress/lzw/reader.go
@@ -19,7 +19,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 )
 
 // Order specifies the bit ordering in an LZW data stream.
@@ -212,8 +211,10 @@ func (d *decoder) flush() {
 	d.o = 0
 }
 
+var errClosed = errors.New("compress/lzw: reader/writer is closed")
+
 func (d *decoder) Close() error {
-	d.err = os.EINVAL // in case any Reads come along
+	d.err = errClosed // in case any Reads come along
 	return nil
 }
 
diff --git a/src/pkg/compress/lzw/writer.go b/src/pkg/compress/lzw/writer.go
index 3f380fadce2..642bfc481e6 100644
--- a/src/pkg/compress/lzw/writer.go
+++ b/src/pkg/compress/lzw/writer.go
@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 )
 
 // A writer is a buffered, flushable writer.
@@ -64,7 +63,7 @@ type encoder struct {
 	// call. It is equal to invalidCode if there was no such call.
 	savedCode uint32
 	// err is the first error encountered during writing. Closing the encoder
-	// will make any future Write calls return os.EINVAL.
+	// will make any future Write calls return errClosed
 	err error
 	// table is the hash table from 20-bit keys to 12-bit values. Each table
 	// entry contains key<<12|val and collisions resolve by linear probing.
@@ -191,13 +190,13 @@ loop:
 // flush e's underlying writer.
 func (e *encoder) Close() error {
 	if e.err != nil {
-		if e.err == os.EINVAL {
+		if e.err == errClosed {
 			return nil
 		}
 		return e.err
 	}
-	// Make any future calls to Write return os.EINVAL.
-	e.err = os.EINVAL
+	// Make any future calls to Write return errClosed.
+	e.err = errClosed
 	// Write the savedCode if valid.
 	if e.savedCode != invalidCode {
 		if err := e.write(e, e.savedCode); err != nil {
diff --git a/src/pkg/compress/lzw/writer_test.go b/src/pkg/compress/lzw/writer_test.go
index 154cdf8090e..d249a09b295 100644
--- a/src/pkg/compress/lzw/writer_test.go
+++ b/src/pkg/compress/lzw/writer_test.go
@@ -50,10 +50,6 @@ func testFile(t *testing.T, fn string, order Order, litWidth int) {
 				return
 			}
 			_, err1 := lzww.Write(b[:n])
-			if err1 == os.EPIPE {
-				// Fail, but do not report the error, as some other (presumably reportable) error broke the pipe.
-				return
-			}
 			if err1 != nil {
 				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
 				return
diff --git a/src/pkg/compress/zlib/writer_test.go b/src/pkg/compress/zlib/writer_test.go
index 32f05ab6856..a71894da320 100644
--- a/src/pkg/compress/zlib/writer_test.go
+++ b/src/pkg/compress/zlib/writer_test.go
@@ -59,10 +59,6 @@ func testLevelDict(t *testing.T, fn string, b0 []byte, level int, d string) {
 		}
 		defer zlibw.Close()
 		_, err = zlibw.Write(b0)
-		if err == os.EPIPE {
-			// Fail, but do not report the error, as some other (presumably reported) error broke the pipe.
-			return
-		}
 		if err != nil {
 			t.Errorf("%s (level=%d, dict=%q): %v", fn, level, d, err)
 			return
diff --git a/src/pkg/crypto/rand/util.go b/src/pkg/crypto/rand/util.go
index b44ae9897ba..fc5fe6c65e9 100644
--- a/src/pkg/crypto/rand/util.go
+++ b/src/pkg/crypto/rand/util.go
@@ -5,16 +5,16 @@
 package rand
 
 import (
+	"errors"
 	"io"
 	"math/big"
-	"os"
 )
 
 // Prime returns a number, p, of the given size, such that p is prime
 // with high probability.
 func Prime(rand io.Reader, bits int) (p *big.Int, err error) {
 	if bits < 1 {
-		err = os.EINVAL
+		err = errors.New("crypto/rand: prime size must be positive")
 	}
 
 	b := uint(bits % 8)
diff --git a/src/pkg/crypto/tls/conn.go b/src/pkg/crypto/tls/conn.go
index f4178e30c58..b8fa2737f67 100644
--- a/src/pkg/crypto/tls/conn.go
+++ b/src/pkg/crypto/tls/conn.go
@@ -93,7 +93,8 @@ func (c *Conn) SetTimeout(nsec int64) error {
 }
 
 // SetReadTimeout sets the time (in nanoseconds) that
-// Read will wait for data before returning os.EAGAIN.
+// Read will wait for data before returning a net.Error
+// with Timeout() == true.
 // Setting nsec == 0 (the default) disables the deadline.
 func (c *Conn) SetReadTimeout(nsec int64) error {
 	return c.conn.SetReadTimeout(nsec)
@@ -737,7 +738,7 @@ func (c *Conn) Write(b []byte) (n int, err error) {
 	return c.writeRecord(recordTypeApplicationData, b)
 }
 
-// Read can be made to time out and return err == os.EAGAIN
+// Read can be made to time out and return a net.Error with Timeout() == true
 // after a fixed time limit; see SetTimeout and SetReadTimeout.
 func (c *Conn) Read(b []byte) (n int, err error) {
 	if err = c.Handshake(); err != nil {
diff --git a/src/pkg/encoding/xml/xml_test.go b/src/pkg/encoding/xml/xml_test.go
index 6c874fadb7a..4c2d196d7b1 100644
--- a/src/pkg/encoding/xml/xml_test.go
+++ b/src/pkg/encoding/xml/xml_test.go
@@ -7,7 +7,6 @@ package xml
 import (
 	"bytes"
 	"io"
-	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -205,7 +204,7 @@ func (d *downCaser) ReadByte() (c byte, err error) {
 
 func (d *downCaser) Read(p []byte) (int, error) {
 	d.t.Fatalf("unexpected Read call on downCaser reader")
-	return 0, os.EINVAL
+	panic("unreachable")
 }
 
 func TestRawTokenAltEncoding(t *testing.T) {
diff --git a/src/pkg/image/tiff/buffer.go b/src/pkg/image/tiff/buffer.go
index ce350738ed8..27533c6047d 100644
--- a/src/pkg/image/tiff/buffer.go
+++ b/src/pkg/image/tiff/buffer.go
@@ -4,10 +4,7 @@
 
 package tiff
 
-import (
-	"io"
-	"os"
-)
+import "io"
 
 // buffer buffers an io.Reader to satisfy io.ReaderAt.
 type buffer struct {
@@ -19,7 +16,7 @@ func (b *buffer) ReadAt(p []byte, off int64) (int, error) {
 	o := int(off)
 	end := o + len(p)
 	if int64(end) != off+int64(len(p)) {
-		return 0, os.EINVAL
+		return 0, io.ErrUnexpectedEOF
 	}
 
 	m := len(b.buf)
diff --git a/src/pkg/log/syslog/syslog.go b/src/pkg/log/syslog/syslog.go
index 26a2f736b17..546bc296a5f 100644
--- a/src/pkg/log/syslog/syslog.go
+++ b/src/pkg/log/syslog/syslog.go
@@ -8,6 +8,7 @@
 package syslog
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -75,7 +76,7 @@ func Dial(network, raddr string, priority Priority, prefix string) (w *Writer, e
 // Write sends a log message to the syslog daemon.
 func (w *Writer) Write(b []byte) (int, error) {
 	if w.priority > LOG_DEBUG || w.priority < LOG_EMERG {
-		return 0, os.EINVAL
+		return 0, errors.New("log/syslog: invalid priority")
 	}
 	return w.conn.writeBytes(w.priority, w.prefix, b)
 }
diff --git a/src/pkg/mime/multipart/formdata.go b/src/pkg/mime/multipart/formdata.go
index d9982e5b9c8..ec643c1476f 100644
--- a/src/pkg/mime/multipart/formdata.go
+++ b/src/pkg/mime/multipart/formdata.go
@@ -160,7 +160,7 @@ type sliceReaderAt []byte
 
 func (r sliceReaderAt) ReadAt(b []byte, off int64) (int, error) {
 	if int(off) >= len(r) || off < 0 {
-		return 0, os.EINVAL
+		return 0, io.ErrUnexpectedEOF
 	}
 	n := copy(b, r[int(off):])
 	return n, nil
diff --git a/src/pkg/net/http/httputil/persist.go b/src/pkg/net/http/httputil/persist.go
index d7b670110c4..1266bd3ad22 100644
--- a/src/pkg/net/http/httputil/persist.go
+++ b/src/pkg/net/http/httputil/persist.go
@@ -22,6 +22,10 @@ var (
 	ErrPipeline   = &http.ProtocolError{"pipeline error"}
 )
 
+// This is an API usage error - the local side is closed.
+// ErrPersistEOF (above) reports that the remote side is closed.
+var errClosed = errors.New("i/o operation on closed connection")
+
 // A ServerConn reads requests and sends responses over an underlying
 // connection, until the HTTP keepalive logic commands an end. ServerConn
 // also allows hijacking the underlying connection by calling Hijack
@@ -108,7 +112,7 @@ func (sc *ServerConn) Read() (req *http.Request, err error) {
 	}
 	if sc.r == nil { // connection closed by user in the meantime
 		defer sc.lk.Unlock()
-		return nil, os.EBADF
+		return nil, errClosed
 	}
 	r := sc.r
 	lastbody := sc.lastbody
@@ -313,7 +317,7 @@ func (cc *ClientConn) Write(req *http.Request) (err error) {
 	}
 	if cc.c == nil { // connection closed by user in the meantime
 		defer cc.lk.Unlock()
-		return os.EBADF
+		return errClosed
 	}
 	c := cc.c
 	if req.Close {
@@ -369,7 +373,7 @@ func (cc *ClientConn) Read(req *http.Request) (resp *http.Response, err error) {
 	}
 	if cc.r == nil { // connection closed by user in the meantime
 		defer cc.lk.Unlock()
-		return nil, os.EBADF
+		return nil, errClosed
 	}
 	r := cc.r
 	lastbody := cc.lastbody
diff --git a/src/pkg/net/http/transport.go b/src/pkg/net/http/transport.go
index da5244b2c12..e622e41f0a2 100644
--- a/src/pkg/net/http/transport.go
+++ b/src/pkg/net/http/transport.go
@@ -504,7 +504,7 @@ func (pc *persistConn) expectingResponse() bool {
 var remoteSideClosedFunc func(error) bool // or nil to use default
 
 func remoteSideClosed(err error) bool {
-	if err == io.EOF || err == os.EINVAL {
+	if err == io.EOF {
 		return true
 	}
 	if remoteSideClosedFunc != nil {
diff --git a/src/pkg/text/tabwriter/tabwriter.go b/src/pkg/text/tabwriter/tabwriter.go
index c136ca2a175..201a685c630 100644
--- a/src/pkg/text/tabwriter/tabwriter.go
+++ b/src/pkg/text/tabwriter/tabwriter.go
@@ -13,7 +13,6 @@ package tabwriter
 import (
 	"bytes"
 	"io"
-	"os"
 	"unicode/utf8"
 )
 
@@ -221,7 +220,7 @@ type osError struct {
 func (b *Writer) write0(buf []byte) {
 	n, err := b.output.Write(buf)
 	if n != len(buf) && err == nil {
-		err = os.EIO
+		err = io.ErrShortWrite
 	}
 	if err != nil {
 		panic(osError{err})
diff --git a/src/pkg/websocket/websocket.go b/src/pkg/websocket/websocket.go
index 1e4036ce391..df4416e22ed 100644
--- a/src/pkg/websocket/websocket.go
+++ b/src/pkg/websocket/websocket.go
@@ -10,12 +10,12 @@ import (
 	"bufio"
 	"crypto/tls"
 	"encoding/json"
+	"errors"
 	"io"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
-	"os"
 	"sync"
 )
 
@@ -243,12 +243,14 @@ func (ws *Conn) RemoteAddr() net.Addr {
 	return &Addr{ws.config.Origin}
 }
 
+var errSetTimeout = errors.New("websocket: cannot set timeout: not using a net.Conn")
+
 // SetTimeout sets the connection's network timeout in nanoseconds.
 func (ws *Conn) SetTimeout(nsec int64) error {
 	if conn, ok := ws.rwc.(net.Conn); ok {
 		return conn.SetTimeout(nsec)
 	}
-	return os.EINVAL
+	return errSetTimeout
 }
 
 // SetReadTimeout sets the connection's network read timeout in nanoseconds.
@@ -256,7 +258,7 @@ func (ws *Conn) SetReadTimeout(nsec int64) error {
 	if conn, ok := ws.rwc.(net.Conn); ok {
 		return conn.SetReadTimeout(nsec)
 	}
-	return os.EINVAL
+	return errSetTimeout
 }
 
 // SetWriteTimeout sets the connection's network write timeout in nanoseconds.
@@ -264,7 +266,7 @@ func (ws *Conn) SetWriteTimeout(nsec int64) error {
 	if conn, ok := ws.rwc.(net.Conn); ok {
 		return conn.SetWriteTimeout(nsec)
 	}
-	return os.EINVAL
+	return errSetTimeout
 }
 
 // Config returns the WebSocket config.