diff --git a/lib/repl.js b/lib/repl.js
index 2c78ce3dff3..ea965d43526 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -16,6 +16,7 @@ var sys = require('sys');
 var Script = process.binding('evals').Script;
 var evalcx = Script.runInContext;
 var path = require("path");
+var fs = require("fs");
 var rl = require('readline');
 var context;
 
@@ -162,7 +163,7 @@ REPLServer.prototype.complete = function (line) {
       completeOn,
       match, filter, i, j, group, c;
 
-  // REPL comments (e.g. ".break").
+  // REPL commands (e.g. ".break").
   var match = null;
   match = line.match(/^\s*(\.\w*)$/);
   if (match) {
@@ -173,6 +174,72 @@ REPLServer.prototype.complete = function (line) {
     }
   }
 
+  // require('...<Tab>')
+  else if (match = line.match(/\brequire\s*\(['"](([\w\.\/-]+\/)?([\w\.\/-]*))/)) {
+    //TODO: suggest require.exts be exposed to be introspec registered extensions?
+    //TODO: suggest include the '.' in exts in internal repr: parity with `path.extname`.
+    var exts = [".js", ".node"];
+    var indexRe = new RegExp('^index(' + exts.map(regexpEscape).join('|') + ')$');
+
+    completeOn = match[1];
+    var subdir = match[2] || "";
+    var filter = match[1];
+    var dir, files, f, name, base, ext, abs, subfiles, s;
+    group = [];
+    for (i = 0; i < require.paths.length; i++) {
+      dir = require.paths[i];
+      if (subdir && subdir[0] === '/') {
+        dir = subdir;
+      } else if (subdir) {
+        dir = path.join(dir, subdir);
+      }
+      try {
+        files = fs.readdirSync(dir);
+      } catch (e) {
+        continue;
+      }
+      for (f = 0; f < files.length; f++) {
+        name = files[f];
+        ext = path.extname(name);
+        base = name.slice(0, -ext.length);
+        if (base.match(/-\d+\.\d+(\.\d+)?/) || name === ".npm") {
+          // Exclude versioned names that 'npm' installs.
+          continue;
+        }
+        if (exts.indexOf(ext) !== -1) {
+          if (!subdir || base !== "index") {
+            group.push(subdir + base);
+          }
+        } else {
+          abs = path.join(dir, name);
+          try {
+            if (fs.statSync(abs).isDirectory()) {
+              group.push(subdir + name + '/');
+              subfiles = fs.readdirSync(abs);
+              for (s = 0; s < subfiles.length; s++) {
+                if (indexRe.test(subfiles[s])) {
+                  group.push(subdir + name);
+                }
+              }
+            }
+          } catch(e) {}
+        }
+      }
+    }
+    if (group.length) {
+      completionGroups.push(group);
+    }
+
+    if (!subdir) {
+      // Kind of lame that this needs to be updated manually.
+      // Intentionally excluding moved modules: posix, utils.
+      var builtinLibs = ['assert', 'buffer', 'child_process', 'crypto', 'dgram',
+        'dns', 'events', 'file', 'freelist', 'fs', 'http', 'net', 'path',
+        'querystring', 'readline', 'repl', 'string_decoder', 'sys', 'tcp', 'url'];
+      completionGroups.push(builtinLibs);
+    }
+  }
+
   // Handle variable member lookup.
   // We support simple chained expressions like the following (no function
   // calls, etc.). That is for simplicity and also because we *eval* that
@@ -348,6 +415,10 @@ function trimWhitespace (cmd) {
   }
 }
 
+function regexpEscape(s) {
+  return s.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
+}
+
 /**
  * Converts commands that use var and function <name>() to use the
  * local exports.context when evaled. This provides a local context