diff --git a/lib/mocha.js b/lib/mocha.js
index d8f9493ff1..0b1cc83f57 100644
--- a/lib/mocha.js
+++ b/lib/mocha.js
@@ -59,6 +59,7 @@ function image(name) {
  *   - `globals` array of accepted globals
  *   - `timeout` timeout in milliseconds
  *   - `ignoreLeaks` ignore global leaks
+ *   - `grep` string or regexp to filter tests with
  *
  * @param {Object} options
  * @api public
@@ -66,6 +67,9 @@ function image(name) {
 
 function Mocha(options) {
   options = options || {};
+  options.grep = 'string' == typeof options.grep
+    ? new RegExp(options.grep)
+    : options.grep;
   this.files = [];
   this.options = options;
   this.suite = new exports.Suite('', new exports.Context);
@@ -154,6 +158,21 @@ Mocha.prototype.growl = function(runner, reporter) {
   });
 };
 
+/**
+ * Add regexp to grep for to the options object
+ *
+ * @param {RegExp} or {String} re
+ * @return {Mocha}
+ * @api public
+ */
+
+Mocha.prototype.grep = function(re){
+  this.options.grep = 'string' == typeof re
+    ? new RegExp(re)
+    : re;
+  return this;
+};
+
 /**
  * Run tests and invoke `fn()` when complete.
  *
diff --git a/test/jsapi/grep.js b/test/jsapi/grep.js
new file mode 100644
index 0000000000..f93cb9093a
--- /dev/null
+++ b/test/jsapi/grep.js
@@ -0,0 +1,44 @@
+var Mocha = require('../../');
+
+describe('Mocha', function(){
+
+  beforeEach(function(){
+    this.reEqual = function(r1, r2){
+      return r1.source === r2.source
+          && r1.global === r2.global
+          && r1.ignoreCase === r2.ignoreCase
+          && r1.multiline === r2.multiline;
+    }
+  })
+
+  describe('constructor options.grep', function(){
+    it('should add a RegExp to the mocha.options object', function(){
+      var mocha = new Mocha({grep:/foo/});
+      this.reEqual(/foo/, mocha.options.grep).should.be.ok;
+    })
+
+    it('should convert grep string to a RegExp', function(){
+      var mocha = new Mocha({grep:'foo'});
+      this.reEqual(/foo/, mocha.options.grep).should.be.ok;
+    })
+  })
+
+  describe('.grep()', function(){
+    it('should add a RegExp to the mocha.options object', function(){
+      var mocha = new Mocha();
+      mocha.grep(/foo/);
+      this.reEqual(/foo/, mocha.options.grep).should.be.ok;
+    })
+
+    it('should convert grep string to a RegExp', function(){
+      var mocha = new Mocha();
+      mocha.grep('foo');
+      this.reEqual(/foo/, mocha.options.grep).should.be.ok;
+    })
+
+    it('should return it\'s parent Mocha object for chainability', function(){
+      var mocha = new Mocha();
+      mocha.grep().should.equal(mocha);
+    })
+  })
+})