diff --git a/spec/observables/forkJoin-spec.js b/spec/observables/forkJoin-spec.js
index a9b7daed42..a2dcc8eb7d 100644
--- a/spec/observables/forkJoin-spec.js
+++ b/spec/observables/forkJoin-spec.js
@@ -1,14 +1,155 @@
-/* globals describe, it, expect */
+/* globals describe, it, expect, lowerCaseO, hot, expectObservable */
 var Rx = require('../../dist/cjs/Rx');
 var Observable = Rx.Observable;
 
 describe('Observable.forkJoin', function () {
-  it('should join the last values of the provided observables into an array', function (done) {
-    Observable.forkJoin(Observable.of(1, 2, 3, 'a'),
-      Observable.of('b'),
-      Observable.of(1, 2, 3, 4, 'c'))
-      .subscribe(function (x) {
-        expect(x).toEqual(['a', 'b', 'c']);
-      }, null, done);
-  });
-});
\ No newline at end of file
+  it('should join the last values of the provided observables into an array', function () {
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('(b|)'),
+               hot('--1--2--3--|')
+    );
+    var expected = '--------------(x|)';
+
+    expectObservable(e1).toBe(expected, {x: ['d', 'b', '3']});
+  });
+
+  it('should accept lowercase-o observables', function () {
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('(b|)'),
+               lowerCaseO('1', '2', '3')
+    );
+    var expected = '--------------(x|)';
+
+    expectObservable(e1).toBe(expected, {x: ['d', 'b', '3']});
+  });
+
+  it('should accept promise', function (done) {
+    var e1 = Observable.forkJoin(
+               Observable.of(1),
+               Promise.resolve(2)
+    );
+
+    e1.subscribe(function (x) {
+      expect(x).toEqual([1,2]);
+    },
+    function (err) {
+      done.fail('should not be called');
+    },
+    done);
+  });
+
+  it('forkJoin n-ary parameters empty', function () {
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('(b|)'),
+               hot('------------------|')
+    );
+    var expected = '------------------|';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin n-ary parameters empty before end', function () {
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('(b|)'),
+               hot('---------|')
+    );
+    var expected = '---------|';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin empty empty', function () {
+    var e1 = Observable.forkJoin(
+               hot('--------------|'),
+               hot('---------|')
+    );
+    var expected = '---------|';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin none', function () {
+    var e1 = Observable.forkJoin();
+    var expected = '|';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin empty return', function () {
+    function selector(x, y) {
+      return x + y;
+    }
+
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('---------|'),
+               selector);
+    var expected = '---------|';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin return return', function () {
+    function selector(x, y) {
+      return x + y;
+    }
+
+    var e1 = Observable.forkJoin(
+               hot('--a--b--c--d--|'),
+               hot('---2-----|'),
+               selector);
+    var expected = '--------------(x|)';
+
+    expectObservable(e1).toBe(expected, {x: 'd2'});
+  });
+
+  it('forkJoin empty throw', function () {
+    var e1 = Observable.forkJoin(
+               hot('------#'),
+               hot('---------|'));
+    var expected = '------#';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin empty throw', function () {
+    function selector(x, y) {
+      return x + y;
+    }
+
+    var e1 = Observable.forkJoin(
+               hot('------#'),
+               hot('---------|'),
+               selector);
+    var expected = '------#';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin return throw', function () {
+    var e1 = Observable.forkJoin(
+               hot('------#'),
+               hot('---a-----|'));
+    var expected = '------#';
+
+    expectObservable(e1).toBe(expected);
+  });
+
+  it('forkJoin return throw', function () {
+    function selector(x, y) {
+      return x + y;
+    }
+
+    var e1 = Observable.forkJoin(
+               hot('------#'),
+               hot('-------b-|'),
+               selector);
+    var expected = '------#';
+
+    expectObservable(e1).toBe(expected);
+  });
+});
diff --git a/src/Observable.ts b/src/Observable.ts
index 2455f5d5e6..d8602e51ec 100644
--- a/src/Observable.ts
+++ b/src/Observable.ts
@@ -138,7 +138,7 @@ export class Observable<T> implements CoreOperators<T>  {
   static concat: <T>(...observables: Array<Observable<any> | Scheduler>) => Observable<T>;
   static defer: <T>(observableFactory: () => Observable<T>) => Observable<T>;
   static empty: <T>(scheduler?: Scheduler) => Observable<T>;
-  static forkJoin: <T>(...observables: Observable<any>[]) => Observable<T>;
+  static forkJoin: (...sources: Array<Observable<any> | Promise<any> | ((...values: Array<any>) => any)>) => Observable<any>;
   static from: <T>(iterable: any, scheduler?: Scheduler) => Observable<T>;
   static fromArray: <T>(array: T[], scheduler?: Scheduler) => Observable<T>;
   static fromEvent: <T>(element: any, eventName: string, selector?: (...args: Array<any>) => T) => Observable<T>;
diff --git a/src/observables/ForkJoinObservable.ts b/src/observables/ForkJoinObservable.ts
index 0d1b3b6829..00b4a2c824 100644
--- a/src/observables/ForkJoinObservable.ts
+++ b/src/observables/ForkJoinObservable.ts
@@ -1,50 +1,96 @@
 import {Observable} from '../Observable';
 import {Subscriber} from '../Subscriber';
+import {PromiseObservable} from './PromiseObservable';
+import {EmptyObservable} from './EmptyObservable';
+import {isPromise} from '../util/isPromise';
 
 export class ForkJoinObservable<T> extends Observable<T> {
-  constructor(private observables: Observable<any>[]) {
-    super();
+  constructor(private sources: Array<Observable<any> |
+                                    Promise<any> |
+                                    ((...values: Array<any>) => any)>) {
+     super();
+   }
+
+  static create(...sources: Array<Observable<any> |
+                                  Promise<any> |
+                                  ((...values: Array<any>) => any)>)
+                                  : Observable<any> {
+    if (sources === null || sources.length === 0) {
+      return new EmptyObservable();
+    }
+    return new ForkJoinObservable(sources);
   }
 
-  static create<R>(...observables: Observable<any>[]): Observable<R> {
-    return new ForkJoinObservable(observables);
+  private getResultSelector(): (...values: Array<any>) => any {
+    const sources = this.sources;
+
+    let resultSelector = sources[sources.length - 1];
+    if (typeof resultSelector !== 'function') {
+      return null;
+    }
+    this.sources.pop();
+    return <(...values: Array<any>) => any>resultSelector;
   }
 
   _subscribe(subscriber: Subscriber<any>) {
-    const observables = this.observables;
-    const len = observables.length;
-    let context = { complete: 0, total: len, values: emptyArray(len) };
+    let resultSelector = this.getResultSelector();
+    const sources = this.sources;
+    const len = sources.length;
+
+    const context = { completed: 0, total: len, values: emptyArray(len), selector: resultSelector };
     for (let i = 0; i < len; i++) {
-      observables[i].subscribe(new AllSubscriber(subscriber, this, i, context));
+      let source = sources[i];
+      if (isPromise(source)) {
+        source = new PromiseObservable(<Promise<any>>source);
+      }
+      (<Observable<any>>source).subscribe(new AllSubscriber(subscriber, i, context));
     }
   }
 }
 
 class AllSubscriber<T> extends Subscriber<T> {
-  private _value: T;
+  private _value: any = null;
 
-  constructor(destination: Subscriber<T>,
-              private parent: ForkJoinObservable<T>,
+  constructor(destination: Subscriber<any>,
               private index: number,
-              private context: { complete: number, total: number, values: any[] }) {
+              private context: { completed: number,
+                                 total: number,
+                                 values: any[],
+                                 selector: (...values: Array<any>) => any }) {
     super(destination);
   }
 
-  _next(value: T) {
+  _next(value: any): void {
     this._value = value;
   }
 
-  _complete() {
+  _complete(): void {
+    const destination = this.destination;
+
+    if (this._value == null) {
+      destination.complete();
+    }
+
     const context = this.context;
+    context.completed++;
     context.values[this.index] = this._value;
-    if (context.values.every(hasValue)) {
-      this.destination.next(context.values);
-      this.destination.complete();
+    const values = context.values;
+
+    if (context.completed !== values.length) {
+      return;
+    }
+
+    if (values.every(hasValue)) {
+      let value = context.selector ? context.selector.apply(this, values) :
+                                     values;
+      destination.next(value);
     }
+
+    destination.complete();
   }
 }
 
-function hasValue(x) {
+function hasValue(x: any): boolean {
   return x !== null;
 }
 
@@ -54,4 +100,4 @@ function emptyArray(len: number): any[] {
     arr.push(null);
   }
   return arr;
-}
\ No newline at end of file
+}
diff --git a/src/observables/PromiseObservable.ts b/src/observables/PromiseObservable.ts
index a015eb5796..75042ed230 100644
--- a/src/observables/PromiseObservable.ts
+++ b/src/observables/PromiseObservable.ts
@@ -13,7 +13,7 @@ export class PromiseObservable<T> extends Observable<T> {
     return new PromiseObservable(promise, scheduler);
   }
 
-  constructor(private promise: Promise<T>, public scheduler: Scheduler) {
+  constructor(private promise: Promise<T>, public scheduler: Scheduler = immediate) {
     super();
   }
 
diff --git a/src/operators/debounce.ts b/src/operators/debounce.ts
index 2fddc22b1d..6d15c009c0 100644
--- a/src/operators/debounce.ts
+++ b/src/operators/debounce.ts
@@ -5,6 +5,7 @@ import {Subscriber} from '../Subscriber';
 import {Subscription} from '../Subscription';
 
 import {tryCatch} from '../util/tryCatch';
+import {isPromise} from '../util/isPromise';
 import {errorObject} from '../util/errorObject';
 
 export function debounce<T>(durationSelector: (value: T) => Observable<any> | Promise<any>): Observable<T> {
@@ -41,8 +42,7 @@ class DebounceSubscriber<T> extends Subscriber<T> {
     if (debounce === errorObject) {
       destination.error(errorObject.e);
     } else {
-      if (typeof debounce.subscribe !== 'function'
-        && typeof debounce.then === 'function') {
+      if (isPromise(debounce)) {
         debounce = PromiseObservable.create(debounce);
       }
 
@@ -102,4 +102,4 @@ class DurationSelectorSubscriber<T> extends Subscriber<T> {
   _complete() {
     this.debounceNext();
   }
-}
\ No newline at end of file
+}
diff --git a/src/util/isPromise.ts b/src/util/isPromise.ts
new file mode 100644
index 0000000000..97d592b649
--- /dev/null
+++ b/src/util/isPromise.ts
@@ -0,0 +1,3 @@
+export function isPromise(value: any): boolean {
+  return value && typeof value.subscribe !== 'function' && typeof value.then === 'function';
+}
\ No newline at end of file