diff --git a/FEATURES.md b/FEATURES.md
index fd28c17940c0..d012284d203e 100644
--- a/FEATURES.md
+++ b/FEATURES.md
@@ -10,21 +10,13 @@ arr.map(x => x * x);
 
 ```javascript
 class Foo extends Bar {
-  constructor() {
+  constructor() { }
 
-  }
-
-  foo() {
-
-  }
+  foo() { }
 
-  get bar() {
-
-  }
-
-  set bar() {
+  get bar() { }
 
-  }
+  set bar() { }
 }
 ```
 
@@ -99,6 +91,18 @@ console.log(`${x} + ${y} = ${x + y}`); // "5 + 10 = 15"
 ```javascript
 ```
 
+## Binary and Octal Literals
+
+```javascript
+0b111110111 === 503; // true
+0o767 === 503; // true
+```
+
+## Iterators
+
+```javascript
+```
+
 ## Constants
 
 ```javascript
diff --git a/README.md b/README.md
index 21e9943d386e..be2504c82f16 100644
--- a/README.md
+++ b/README.md
@@ -24,29 +24,31 @@
 
  - **Fast** - [10x faster than Traceur](#performance).
  - **Extensive** - with Browserify support, Node API, Connect Middleware and a CLI.
- - **Lossless** - source map support so you can debug your compiled code with ease.
+ - **Lossless** - **source map support** so you can debug your compiled code with ease.
  - **Compact** - maps directly to the equivalent ES5 with **no runtime required**.
  - **Concise** - does not pollute scope with unneccesary variables.
 
-## Features
-
-| Name                                                                 | Implemented |
-| -------------------------------------------------------------------- | ----------- |
-| [Arrow functions](FEATURES.md#arrow-functions)                       | ✓           |
-| [Classes](FEATURES.md#classes)                                       | ✓           |
-| [Default parameters](FEATURES.md#default-parameters)                 | ✓           |
-| [Spread](FEATURES.md#spread)                                         | ✓           |
-| [Block binding](FEATURES.md#block-binding)                           | ✓           |
-| [Property method assignment](FEATURES.md#property-method-assignment) | ✓           |
-| [Rest parameters](FEATURES.md#rest-parameters)                       | ✓           |
-| [Template literals](FEATURES.md#template-literals)                   | ✓           |
-| [Modules](FEATURES.md#modules)                                       | ✓           |
-| [Property name shorthand](FEATURES.md#property-name-shorthand)       | ✓           |
-| [Computed property names](FEATURES.md#computed-property-names)       | ✓           |
-| [Constants](FEATURES.md#constants)                                   | ✓           |
-| [Destructuring assignment](FEATURES.md#destructuring-assignment)     |             |
-| [Array comprehension](FEATURES.md#array-comprehension)               |             |
-| [Generators](FEATURES.md#generators)                                 |             |
+## [Features](FEATURES.md)
+
+| Name                                                                 | Implemented | [Polyfill](#polyfill) |
+| -------------------------------------------------------------------- | ----------- | --------------------- |
+| [Arrow functions](FEATURES.md#arrow-functions)                       | ✓           |                       |
+| [Classes](FEATURES.md#classes)                                       | ✓           |                       |
+| [Default parameters](FEATURES.md#default-parameters)                 | ✓           |                       |
+| [Spread](FEATURES.md#spread)                                         | ✓           |                       |
+| [Block binding](FEATURES.md#block-binding)                           | ✓           |                       |
+| [Property method assignment](FEATURES.md#property-method-assignment) | ✓           |                       |
+| [Rest parameters](FEATURES.md#rest-parameters)                       | ✓           |                       |
+| [Template literals](FEATURES.md#template-literals)                   | ✓           |                       |
+| [Modules](FEATURES.md#modules)                                       | ✓           |                       |
+| [Property name shorthand](FEATURES.md#property-name-shorthand)       | ✓           |                       |
+| [Computed property names](FEATURES.md#computed-property-names)       | ✓           |                       |
+| [Constants](FEATURES.md#constants)                                   | ✓           |                       |
+| [Binary and Octal Literals](FEATURES.md#binary-and-octal-literals)   | ✓           |                       |
+| [Iterators](FEATURES.md#iterators)                                   |             | ✓                     |
+| [Destructuring assignment](FEATURES.md#destructuring-assignment)     |             |                       |
+| [Array comprehension](FEATURES.md#array-comprehension)               |             |                       |
+| [Generators](FEATURES.md#generators)                                 |             |                       |
 
 ## Installation
 
@@ -147,6 +149,14 @@ browserify()
   .pipe(fs.createWriteStream("bundle.js"));
 ```
 
+## Caveats
+
+### Polyfill
+
+### Classes
+
+Cannot subclass built-ins such as `Date`, `Array`, `DOM` etc.
+
 ## Comparison to Traceur
 
 ### Performance
diff --git a/lib/6to5/templates/for-of.js b/lib/6to5/templates/for-of.js
new file mode 100644
index 000000000000..916c6c8eb610
--- /dev/null
+++ b/lib/6to5/templates/for-of.js
@@ -0,0 +1,3 @@
+for (var ITERATOR_KEY = OBJECT[Symbol.iterator](), STEP_KEY; !(STEP_KEY = ITERATOR_KEY.next()).done; ) {
+  var KEY = STEP_KEY.value;
+}
diff --git a/lib/6to5/transform.js b/lib/6to5/transform.js
index 5cbdc71b5144..517ef046c788 100644
--- a/lib/6to5/transform.js
+++ b/lib/6to5/transform.js
@@ -30,6 +30,8 @@ var transform = module.exports = function (code, opts) {
     }
   });
 
+  var generateUid = util.buildUidGenerator();
+
   _.each(transform.transformers, function (transformer, name) {
     var blacklist = opts.blacklist;
     if (blacklist.length && _.contains(blacklist, name)) return;
@@ -37,7 +39,7 @@ var transform = module.exports = function (code, opts) {
     var whitelist = opts.whitelist;
     if (whitelist.length && !_.contains(whitelist, name)) return;
 
-    transform._runTransformer(transformer, tree, opts);
+    transform._runTransformer(transformer, tree, opts, generateUid);
   });
 
   var genOpts = {
@@ -64,14 +66,14 @@ var transform = module.exports = function (code, opts) {
   }
 };
 
-transform._runTransformer = function (transformer, tree, opts) {
+transform._runTransformer = function (transformer, tree, opts, generateUid) {
   if (transformer.Program) transformer.Program(tree, opts);
 
   traverse.replace(tree, function (node, parent) {
     var fn = transformer[node.type] || transformer.all;
     if (!fn) return;
 
-    return fn(node, parent, opts);
+    return fn(node, parent, opts, generateUid);
   });
 };
 
@@ -109,5 +111,6 @@ transform.transformers = {
   generators:               require("./transformers/generators"),
   blockBinding:             require("./transformers/block-binding"),
   modules:                  require("./transformers/modules"),
-  restParameters:           require("./transformers/rest-parameters")
+  restParameters:           require("./transformers/rest-parameters"),
+  iterators:                require("./transformers/iterators")
 };
diff --git a/lib/6to5/transformers/arrow-functions.js b/lib/6to5/transformers/arrow-functions.js
index 6fbe9893718b..558cd8388d60 100644
--- a/lib/6to5/transformers/arrow-functions.js
+++ b/lib/6to5/transformers/arrow-functions.js
@@ -3,6 +3,8 @@ var util     = require("../util");
 
 exports.ArrowFunctionExpression = function (node) {
   var body = node.body;
+
+  // expression body
   if (body.type !== "BlockStatement") {
     body = {
       type: "BlockStatement",
diff --git a/lib/6to5/transformers/block-binding.js b/lib/6to5/transformers/block-binding.js
index a6a4b50758a9..ee53ae3a3818 100644
--- a/lib/6to5/transformers/block-binding.js
+++ b/lib/6to5/transformers/block-binding.js
@@ -35,6 +35,7 @@ exports.BlockStatement = function (node, parent) {
   node.body = buildNode(node.body);
 };
 
+exports.ForOfStatement =
 exports.ForInStatement = function (node) {
   if (isLet(node.left)) return buildNode(node);
 };
diff --git a/lib/6to5/transformers/constants.js b/lib/6to5/transformers/constants.js
index 485285d04749..65d579444b87 100644
--- a/lib/6to5/transformers/constants.js
+++ b/lib/6to5/transformers/constants.js
@@ -5,6 +5,7 @@ var _        = require("lodash");
 exports.Program =
 exports.BlockStatement =
 exports.ForInStatement =
+exports.ForOfStatement =
 exports.ForStatement = function (node) {
   var constants = [];
 
diff --git a/lib/6to5/transformers/iterators.js b/lib/6to5/transformers/iterators.js
new file mode 100644
index 000000000000..b1ac7426ea23
--- /dev/null
+++ b/lib/6to5/transformers/iterators.js
@@ -0,0 +1,20 @@
+var util = require("../util");
+
+exports.ForOfStatement = function (node, parent, opts, generateUid) {
+  var node2 = util.template("for-of", {
+    ITERATOR_KEY: generateUid("iterator"),
+    STEP_KEY: generateUid("step"),
+
+    KEY: node.left.declarations[0].id,
+    OBJECT: node.right
+  });
+
+  var block = node2.body;
+
+  var declar = block.body[0];
+  declar.kind = node.left.kind;
+
+  block.body = block.body.concat(node.body.body);
+
+  return node2;
+};
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 18d0d92019fe..9eadafcf1ba4 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -47,6 +47,19 @@ exports.canCompile = function (filename) {
   return path.extname(filename) === ".js";
 };
 
+exports.buildUidGenerator = function () {
+  var ids = {};
+
+  return function (name) {
+    var i = ids[name] || 0;
+
+    var id = "_" + name;
+    if (i > 0) id += i;
+    ids[name] = i + 1;
+    return id;
+  };
+};
+
 exports.sourceMapToComment = function (map) {
   var json = JSON.stringify(map);
   var base64 = new Buffer(json).toString("base64");
diff --git a/test/fixtures/arrow-functions/expression/actual.js b/test/fixtures/arrow-functions/expression/actual.js
new file mode 100644
index 000000000000..adc984840775
--- /dev/null
+++ b/test/fixtures/arrow-functions/expression/actual.js
@@ -0,0 +1 @@
+arr.map(x => x * x);
diff --git a/test/fixtures/arrow-functions/expression/expected.js b/test/fixtures/arrow-functions/expression/expected.js
new file mode 100644
index 000000000000..e2bcfeb4cdbd
--- /dev/null
+++ b/test/fixtures/arrow-functions/expression/expected.js
@@ -0,0 +1,3 @@
+arr.map(function (x) {
+  return x * x;
+});
diff --git a/test/fixtures/arrow-functions/statement/actual.js b/test/fixtures/arrow-functions/statement/actual.js
new file mode 100644
index 000000000000..668b7483d24d
--- /dev/null
+++ b/test/fixtures/arrow-functions/statement/actual.js
@@ -0,0 +1,5 @@
+nums.forEach(v => {
+  if (v % 5 === 0) {
+    fives.push(v);
+  }
+});
diff --git a/test/fixtures/arrow-functions/statement/expected.js b/test/fixtures/arrow-functions/statement/expected.js
new file mode 100644
index 000000000000..40ecaad5725c
--- /dev/null
+++ b/test/fixtures/arrow-functions/statement/expected.js
@@ -0,0 +1,5 @@
+nums.forEach(function (v) {
+  if (v % 5 === 0) {
+    fives.push(v);
+  }
+});
diff --git a/test/fixtures/iterators/for-of-let/actual.js b/test/fixtures/iterators/for-of-let/actual.js
new file mode 100644
index 000000000000..f1e32392def1
--- /dev/null
+++ b/test/fixtures/iterators/for-of-let/actual.js
@@ -0,0 +1,3 @@
+for (let i of arr) {
+
+}
diff --git a/test/fixtures/iterators/for-of-let/expected.js b/test/fixtures/iterators/for-of-let/expected.js
new file mode 100644
index 000000000000..ee144f69328f
--- /dev/null
+++ b/test/fixtures/iterators/for-of-let/expected.js
@@ -0,0 +1,5 @@
+(function () {
+  for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+    var i = _step.value;
+  }
+}());
diff --git a/test/fixtures/iterators/for-of/actual.js b/test/fixtures/iterators/for-of/actual.js
new file mode 100644
index 000000000000..48e5f59b2c6b
--- /dev/null
+++ b/test/fixtures/iterators/for-of/actual.js
@@ -0,0 +1,3 @@
+for (var i of arr) {
+
+}
diff --git a/test/fixtures/iterators/for-of/expected.js b/test/fixtures/iterators/for-of/expected.js
new file mode 100644
index 000000000000..7bfbba16366b
--- /dev/null
+++ b/test/fixtures/iterators/for-of/expected.js
@@ -0,0 +1,3 @@
+for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done; ) {
+  var i = _step.value;
+}