diff --git a/src/R3/Factories/Return.cs b/src/R3/Factories/Return.cs
index 4f93fb7c..e05ef237 100644
--- a/src/R3/Factories/Return.cs
+++ b/src/R3/Factories/Return.cs
@@ -1,32 +1,28 @@
-using System;
-
-namespace R3;
+namespace R3;
 
 public static partial class Observable
 {
-    // TODO: CancellationToken?
-
     public static Observable<T> Return<T>(T value)
     {
         return new ImmediateScheduleReturn<T>(value); // immediate
     }
 
-    public static Observable<T> Return<T>(T value, TimeProvider timeProvider)
+    public static Observable<T> Return<T>(T value, TimeProvider timeProvider, CancellationToken cancellationToken = default)
     {
-        return Return(value, TimeSpan.Zero, timeProvider);
+        return Return(value, TimeSpan.Zero, timeProvider, cancellationToken);
     }
 
-    public static Observable<T> Return<T>(T value, TimeSpan dueTime, TimeProvider timeProvider)
+    public static Observable<T> Return<T>(T value, TimeSpan dueTime, TimeProvider timeProvider, CancellationToken cancellationToken = default)
     {
         if (dueTime == TimeSpan.Zero)
         {
             if (timeProvider == TimeProvider.System)
             {
-                return new ThreadPoolScheduleReturn<T>(value); // optimize for SystemTimeProvidr, use ThreadPool.UnsafeQueueUserWorkItem
+                return new ThreadPoolScheduleReturn<T>(value, cancellationToken); // optimize for SystemTimeProvidr, use ThreadPool.UnsafeQueueUserWorkItem
             }
         }
 
-        return new Return<T>(value, dueTime.Normalize(), timeProvider); // use ITimer
+        return new Return<T>(value, dueTime.Normalize(), timeProvider, cancellationToken); // use ITimer
     }
 
     // Optimized case
@@ -53,27 +49,37 @@ public static Observable<int> Return(int value)
 
     // util
 
-    public static Observable<Unit> Yield()
+    public static Observable<Unit> Yield(CancellationToken cancellationToken = default)
     {
-        return new ThreadPoolScheduleReturn<Unit>(default);
+        return new ThreadPoolScheduleReturn<Unit>(default, cancellationToken);
     }
 
-    public static Observable<Unit> Yield(TimeProvider timeProvider)
+    public static Observable<Unit> Yield(TimeProvider timeProvider, CancellationToken cancellationToken = default)
     {
         if (timeProvider == TimeProvider.System)
         {
-            return new ThreadPoolScheduleReturn<Unit>(default);
+            return new ThreadPoolScheduleReturn<Unit>(default, cancellationToken);
         }
-        return new Return<Unit>(default, TimeSpan.Zero, timeProvider);
+        return new Return<Unit>(default, TimeSpan.Zero, timeProvider, cancellationToken);
     }
 }
 
-internal sealed class Return<T>(T value, TimeSpan dueTime, TimeProvider timeProvider) : Observable<T>
+internal sealed class Return<T>(T value, TimeSpan dueTime, TimeProvider timeProvider, CancellationToken cancellationToken) : Observable<T>
 {
     protected override IDisposable SubscribeCore(Observer<T> observer)
     {
         var method = new _Return(value, observer);
         method.Timer = timeProvider.CreateStoppedTimer(_Return.timerCallback, method);
+
+        if (cancellationToken.CanBeCanceled)
+        {
+            method.cancellationTokenRegistration = cancellationToken.UnsafeRegister(static state =>
+            {
+                var s = (_Return)state!;
+                s.CompleteDispose();
+            }, method);
+        }
+
         method.Timer.InvokeOnce(dueTime);
         return method;
     }
@@ -82,6 +88,8 @@ sealed class _Return(T value, Observer<T> observer) : IDisposable
     {
         public static readonly TimerCallback timerCallback = NextTick;
 
+        internal CancellationTokenRegistration cancellationTokenRegistration;
+
         readonly T value = value;
         readonly Observer<T> observer = observer;
 
@@ -94,8 +102,15 @@ static void NextTick(object? state)
             self.observer.OnCompleted();
         }
 
+        public void CompleteDispose()
+        {
+            observer.OnCompleted();
+            Dispose();
+        }
+
         public void Dispose()
         {
+            cancellationTokenRegistration.Dispose();
             Timer?.Dispose();
             Timer = null;
         }
@@ -112,11 +127,21 @@ protected override IDisposable SubscribeCore(Observer<T> observer)
     }
 }
 
-internal sealed class ThreadPoolScheduleReturn<T>(T value) : Observable<T>
+internal sealed class ThreadPoolScheduleReturn<T>(T value, CancellationToken cancellationToken) : Observable<T>
 {
     protected override IDisposable SubscribeCore(Observer<T> observer)
     {
         var method = new _Return(value, observer);
+
+        if (cancellationToken.CanBeCanceled)
+        {
+            method.cancellationTokenRegistration = cancellationToken.UnsafeRegister(static state =>
+            {
+                var s = (_Return)state!;
+                s.CompleteDispose();
+            }, method);
+        }
+
         ThreadPool.UnsafeQueueUserWorkItem(method, preferLocal: false);
         return method;
     }
@@ -125,6 +150,8 @@ sealed class _Return(T value, Observer<T> observer) : IDisposable, IThreadPoolWo
     {
         bool stop;
 
+        internal CancellationTokenRegistration cancellationTokenRegistration;
+
         public void Execute()
         {
             if (stop) return;
@@ -133,8 +160,15 @@ public void Execute()
             observer.OnCompleted();
         }
 
+        public void CompleteDispose()
+        {
+            observer.OnCompleted();
+            Dispose();
+        }
+
         public void Dispose()
         {
+            cancellationTokenRegistration.Dispose();
             stop = true;
         }
     }