diff --git a/observer.go b/observer.go
index decce191..450db68d 100644
--- a/observer.go
+++ b/observer.go
@@ -1,8 +1,6 @@
 package rxgo
 
 import (
-	"sync"
-
 	"github.com/reactivex/rxgo/options"
 
 	"github.com/reactivex/rxgo/handlers"
@@ -25,8 +23,7 @@ type Observer interface {
 }
 
 type observer struct {
-	disposedMutex        sync.Mutex
-	disposed             bool
+	disposed             chan struct{}
 	nextHandler          handlers.NextFunc
 	errHandler           handlers.ErrFunc
 	doneHandler          handlers.DoneFunc
@@ -55,7 +52,9 @@ func (o *observer) getChannel() chan interface{} {
 // NewObserver constructs a new Observer instance with default Observer and accept
 // any number of EventHandler
 func NewObserver(eventHandlers ...handlers.EventHandler) Observer {
-	ob := observer{}
+	ob := observer{
+		disposed: make(chan struct{}),
+	}
 
 	if len(eventHandlers) > 0 {
 		for _, handler := range eventHandlers {
@@ -98,24 +97,21 @@ func (o *observer) Handle(item interface{}) {
 }
 
 func (o *observer) Dispose() {
-	o.disposedMutex.Lock()
-	o.disposed = true
-	o.disposedMutex.Unlock()
+	close(o.disposed)
 }
 
 func (o *observer) IsDisposed() bool {
-	o.disposedMutex.Lock()
-	defer o.disposedMutex.Unlock()
-	return o.disposed
+	select {
+	case <-o.disposed:
+		return true
+	default:
+		return false
+	}
 }
 
 // OnNext applies Observer's NextHandler to an Item
 func (o *observer) OnNext(item interface{}) {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-
-	if !disposed {
+	if !o.IsDisposed() {
 		switch item := item.(type) {
 		case error:
 			return
@@ -131,10 +127,7 @@ func (o *observer) OnNext(item interface{}) {
 
 // OnError applies Observer's ErrHandler to an error
 func (o *observer) OnError(err error) {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
+	if !o.IsDisposed() {
 		if o.errHandler != nil {
 			o.errHandler(err)
 			o.Dispose()
@@ -150,10 +143,7 @@ func (o *observer) OnError(err error) {
 
 // OnDone terminates the Observer's internal Observable
 func (o *observer) OnDone() {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
+	if !o.IsDisposed() {
 		if o.doneHandler != nil {
 			o.doneHandler()
 			o.Dispose()
@@ -169,10 +159,7 @@ func (o *observer) OnDone() {
 
 // OnDone terminates the Observer's internal Observable
 func (o *observer) Block() error {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
+	if !o.IsDisposed() {
 		for v := range o.done {
 			return v
 		}
diff --git a/observer_test.go b/observer_test.go
index f4a4282c..31d10883 100644
--- a/observer_test.go
+++ b/observer_test.go
@@ -56,3 +56,14 @@ func TestHandle(t *testing.T) {
 	ob.Handle(errors.New(""))
 	assert.Equal(t, 7, i)
 }
+
+func BenchmarkObserver_IsDisposed(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		o := NewObserver()
+		for i := 0; i < 10; i++ {
+			o.IsDisposed()
+		}
+		o.Dispose()
+		o.IsDisposed()
+	}
+}
diff --git a/singleobserver.go b/singleobserver.go
index 9bda0020..0672ae56 100644
--- a/singleobserver.go
+++ b/singleobserver.go
@@ -1,8 +1,6 @@
 package rxgo
 
 import (
-	"sync"
-
 	"github.com/reactivex/rxgo/handlers"
 )
 
@@ -11,24 +9,24 @@ type SingleObserver interface {
 	handlers.EventHandler
 	Disposable
 
+	Block() (interface{}, error)
 	OnSuccess(item interface{})
 	OnError(err error)
-
-	Block() (interface{}, error)
 }
 
 type singleObserver struct {
-	disposedMutex sync.Mutex
-	disposed      bool
-	nextHandler   handlers.NextFunc
-	errHandler    handlers.ErrFunc
-	done          chan interface{}
+	disposed    chan struct{}
+	nextHandler handlers.NextFunc
+	errHandler  handlers.ErrFunc
+	done        chan interface{}
 }
 
 // NewSingleObserver constructs a new SingleObserver instance with default SingleObserver and accept
 // any number of EventHandler
 func NewSingleObserver(eventHandlers ...handlers.EventHandler) SingleObserver {
-	ob := singleObserver{}
+	ob := singleObserver{
+		disposed: make(chan struct{}),
+	}
 
 	if len(eventHandlers) > 0 {
 		for _, handler := range eventHandlers {
@@ -66,23 +64,36 @@ func (o *singleObserver) Handle(item interface{}) {
 }
 
 func (o *singleObserver) Dispose() {
-	o.disposedMutex.Lock()
-	o.disposed = true
-	o.disposedMutex.Unlock()
+	close(o.disposed)
 }
 
 func (o *singleObserver) IsDisposed() bool {
-	o.disposedMutex.Lock()
-	defer o.disposedMutex.Unlock()
-	return o.disposed
+	select {
+	case <-o.disposed:
+		return true
+	default:
+		return false
+	}
+}
+
+// Block terminates the SingleObserver's internal Observable
+func (o *singleObserver) Block() (interface{}, error) {
+	if !o.IsDisposed() {
+		for v := range o.done {
+			switch v := v.(type) {
+			case error:
+				return nil, v
+			default:
+				return v, nil
+			}
+		}
+	}
+	return nil, nil
 }
 
 // OnNext applies SingleObserver's NextHandler to an Item
 func (o *singleObserver) OnSuccess(item interface{}) {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
+	if !o.IsDisposed() {
 		switch item := item.(type) {
 		case error:
 			return
@@ -103,10 +114,7 @@ func (o *singleObserver) OnSuccess(item interface{}) {
 
 // OnError applies SingleObserver's ErrHandler to an error
 func (o *singleObserver) OnError(err error) {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
+	if !o.IsDisposed() {
 		if o.errHandler != nil {
 			o.errHandler(err)
 			o.Dispose()
@@ -119,21 +127,3 @@ func (o *singleObserver) OnError(err error) {
 		// TODO
 	}
 }
-
-// Block terminates the SingleObserver's internal Observable
-func (o *singleObserver) Block() (interface{}, error) {
-	o.disposedMutex.Lock()
-	disposed := o.disposed
-	o.disposedMutex.Unlock()
-	if !disposed {
-		for v := range o.done {
-			switch v := v.(type) {
-			case error:
-				return nil, v
-			default:
-				return v, nil
-			}
-		}
-	}
-	return nil, nil
-}
diff --git a/singleobserver_test.go b/singleobserver_test.go
index bbcfd43c..5e1feb20 100644
--- a/singleobserver_test.go
+++ b/singleobserver_test.go
@@ -55,3 +55,14 @@ func TestSingleObserverHandleWithError(t *testing.T) {
 	singleObserver.Handle(errors.New(""))
 	assert.Equal(t, int64(10), got)
 }
+
+func BenchmarkSingleObserver_IsDisposed(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		o := NewSingleObserver()
+		for i := 0; i < 10; i++ {
+			o.IsDisposed()
+		}
+		o.Dispose()
+		o.IsDisposed()
+	}
+}