diff --git a/cmd/godoc/godoc_test.go b/cmd/godoc/godoc_test.go
index 39ca16ae..095bed55 100644
--- a/cmd/godoc/godoc_test.go
+++ b/cmd/godoc/godoc_test.go
@@ -152,11 +152,49 @@ func TestWeb(t *testing.T) {
 	}
 	defer cmd.Process.Kill()
 	waitForServer(t, addr)
-	tests := []struct{ path, substr string }{
-		{"/", "Go is an open source programming language"},
-		{"/pkg/fmt/", "Package fmt implements formatted I/O"},
-		{"/src/fmt/", "scan_test.go"},
-		{"/src/fmt/print.go", "// Println formats using"},
+	tests := []struct {
+		path      string
+		match     []string
+		dontmatch []string
+	}{
+		{
+			path:  "/",
+			match: []string{"Go is an open source programming language"},
+		},
+		{
+			path:  "/pkg/fmt/",
+			match: []string{"Package fmt implements formatted I/O"},
+		},
+		{
+			path:  "/src/fmt/",
+			match: []string{"scan_test.go"},
+		},
+		{
+			path:  "/src/fmt/print.go",
+			match: []string{"// Println formats using"},
+		},
+		{
+			path: "/pkg",
+			match: []string{
+				"Standard library",
+				"Package fmt implements formatted I/O",
+			},
+			dontmatch: []string{
+				"internal/syscall",
+				"cmd/gc",
+			},
+		},
+		{
+			path: "/pkg/?m=all",
+			match: []string{
+				"Standard library",
+				"Package fmt implements formatted I/O",
+				"internal/syscall",
+			},
+			dontmatch: []string{
+				"cmd/gc",
+			},
+		},
 	}
 	for _, test := range tests {
 		url := fmt.Sprintf("http://%s%s", addr, test.path)
@@ -170,9 +208,21 @@ func TestWeb(t *testing.T) {
 		if err != nil {
 			t.Errorf("GET %s: failed to read body: %s (response: %v)", url, err, resp)
 		}
-		if bytes.Index(body, []byte(test.substr)) < 0 {
-			t.Errorf("GET %s: want substring %q in body, got:\n%s",
-				url, test.substr, string(body))
+		isErr := false
+		for _, substr := range test.match {
+			if !bytes.Contains(body, []byte(substr)) {
+				t.Errorf("GET %s: wanted substring %q in body", url, substr)
+				isErr = true
+			}
+		}
+		for _, substr := range test.dontmatch {
+			if bytes.Contains(body, []byte(substr)) {
+				t.Errorf("GET %s: didn't want substring %q in body", url, substr)
+				isErr = true
+			}
+		}
+		if isErr {
+			t.Errorf("GET %s: got:\n%s", url, body)
 		}
 	}
 }
diff --git a/godoc/cmdline_test.go b/godoc/cmdline_test.go
index 2228a6ae..64e1c442 100644
--- a/godoc/cmdline_test.go
+++ b/godoc/cmdline_test.go
@@ -194,8 +194,19 @@ package main
 	fs.Bind("/", mfs, "/", vfs.BindReplace)
 	c := NewCorpus(fs)
 	p := &Presentation{Corpus: c}
-	p.cmdHandler = handlerServer{p, c, "/cmd/", "/src/cmd"}
-	p.pkgHandler = handlerServer{p, c, "/pkg/", "/src"}
+	p.cmdHandler = handlerServer{
+		p:       p,
+		c:       c,
+		pattern: "/cmd/",
+		fsRoot:  "/src/cmd",
+	}
+	p.pkgHandler = handlerServer{
+		p:       p,
+		c:       c,
+		pattern: "/pkg/",
+		fsRoot:  "/src",
+		exclude: []string{"/src/cmd"},
+	}
 	p.initFuncMap()
 	p.PackageText = template.Must(template.New("PackageText").Funcs(p.FuncMap()).Parse(`{{$info := .}}{{$filtered := .IsFiltered}}{{if $filtered}}{{range .PAst}}{{range .Decls}}{{node $info .}}{{end}}{{end}}{{else}}{{with .PAst}}{{range $filename, $ast := .}}{{$filename}}:
 {{node $ $ast}}{{end}}{{end}}{{end}}{{with .PDoc}}{{if $.IsMain}}COMMAND {{.Doc}}{{else}}PACKAGE {{.Doc}}{{end}}{{with .Funcs}}
diff --git a/godoc/dirtrees.go b/godoc/dirtrees.go
index c38d3b2c..af8b02f0 100644
--- a/godoc/dirtrees.go
+++ b/godoc/dirtrees.go
@@ -280,8 +280,10 @@ type DirList struct {
 
 // listing creates a (linear) directory listing from a directory tree.
 // If skipRoot is set, the root directory itself is excluded from the list.
+// If filter is set, only the directory entries whose paths match the filter
+// are included.
 //
-func (root *Directory) listing(skipRoot bool) *DirList {
+func (root *Directory) listing(skipRoot bool, filter func(string) bool) *DirList {
 	if root == nil {
 		return nil
 	}
@@ -306,10 +308,12 @@ func (root *Directory) listing(skipRoot bool) *DirList {
 	}
 
 	// create list
-	list := make([]DirEntry, n)
-	i := 0
+	list := make([]DirEntry, 0, n)
 	for d := range root.iter(skipRoot) {
-		p := &list[i]
+		if filter != nil && !filter(d.Path) {
+			continue
+		}
+		var p DirEntry
 		p.Depth = d.Depth - minDepth
 		p.Height = maxHeight - p.Depth
 		// the path is relative to root.Path - remove the root.Path
@@ -322,7 +326,7 @@ func (root *Directory) listing(skipRoot bool) *DirList {
 		p.Name = d.Name
 		p.HasPkg = d.HasPkg
 		p.Synopsis = d.Synopsis
-		i++
+		list = append(list, p)
 	}
 
 	return &DirList{maxHeight, list}
diff --git a/godoc/pres.go b/godoc/pres.go
index 42c40f02..2bf71f18 100644
--- a/godoc/pres.go
+++ b/godoc/pres.go
@@ -115,8 +115,19 @@ func NewPresentation(c *Corpus) *Presentation {
 			(*Presentation).SearchResultTxt,
 		},
 	}
-	p.cmdHandler = handlerServer{p, c, "/cmd/", "/src/cmd"}
-	p.pkgHandler = handlerServer{p, c, "/pkg/", "/src"}
+	p.cmdHandler = handlerServer{
+		p:       p,
+		c:       c,
+		pattern: "/cmd/",
+		fsRoot:  "/src/cmd",
+	}
+	p.pkgHandler = handlerServer{
+		p:       p,
+		c:       c,
+		pattern: "/pkg/",
+		fsRoot:  "/src",
+		exclude: []string{"/src/cmd"},
+	}
 	p.cmdHandler.registerWithMux(p.mux)
 	p.pkgHandler.registerWithMux(p.mux)
 	p.mux.HandleFunc("/", p.ServeFile)
diff --git a/godoc/server.go b/godoc/server.go
index e81c6737..0373679c 100644
--- a/godoc/server.go
+++ b/godoc/server.go
@@ -36,9 +36,10 @@ import (
 // This should probably merge into something else.
 type handlerServer struct {
 	p       *Presentation
-	c       *Corpus // copy of p.Corpus
-	pattern string  // url pattern; e.g. "/pkg/"
-	fsRoot  string  // file system root to which the pattern is mapped
+	c       *Corpus  // copy of p.Corpus
+	pattern string   // url pattern; e.g. "/pkg/"
+	fsRoot  string   // file system root to which the pattern is mapped; e.g. "/src"
+	exclude []string // file system paths to exclude; e.g. "/src/cmd"
 }
 
 func (s *handlerServer) registerWithMux(mux *http.ServeMux) {
@@ -66,7 +67,14 @@ func (h *handlerServer) GetPageInfo(abspath, relpath string, mode PageInfoMode)
 	ctxt := build.Default
 	ctxt.IsAbsPath = pathpkg.IsAbs
 	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
-		return h.c.fs.ReadDir(filepath.ToSlash(dir))
+		f, err := h.c.fs.ReadDir(filepath.ToSlash(dir))
+		filtered := make([]os.FileInfo, 0, len(f))
+		for _, i := range f {
+			if mode&NoFiltering != 0 || i.Name() != "internal" {
+				filtered = append(filtered, i)
+			}
+		}
+		return filtered, err
 	}
 	ctxt.OpenFile = func(name string) (r io.ReadCloser, err error) {
 		data, err := vfs.ReadFile(h.c.fs, filepath.ToSlash(name))
@@ -188,13 +196,35 @@ func (h *handlerServer) GetPageInfo(abspath, relpath string, mode PageInfoMode)
 		dir = h.c.newDirectory(abspath, 1)
 		timestamp = time.Now()
 	}
-	info.Dirs = dir.listing(true)
+	info.Dirs = dir.listing(true, func(path string) bool { return h.includePath(path, mode) })
 	info.DirTime = timestamp
 	info.DirFlat = mode&FlatDir != 0
 
 	return info
 }
 
+func (h *handlerServer) includePath(path string, mode PageInfoMode) (r bool) {
+	// if the path is under one of the exclusion paths, don't list.
+	for _, e := range h.exclude {
+		if strings.HasPrefix(path, e) {
+			return false
+		}
+	}
+
+	// if the path includes 'internal', don't list unless we are in the NoFiltering mode.
+	if mode&NoFiltering != 0 {
+		return true
+	}
+	if strings.Contains(path, "internal") {
+		for _, c := range strings.Split(path, string(os.PathSeparator)) {
+			if c == "internal" {
+				return false
+			}
+		}
+	}
+	return true
+}
+
 type funcsByName []*doc.Func
 
 func (s funcsByName) Len() int           { return len(s) }