diff --git a/integration-testing/src/main/java/com/google/net/stubby/testing/integration/AbstractTransportTest.java b/integration-testing/src/main/java/com/google/net/stubby/testing/integration/AbstractTransportTest.java
index 6239ca2..effdaf9 100644
--- a/integration-testing/src/main/java/com/google/net/stubby/testing/integration/AbstractTransportTest.java
+++ b/integration-testing/src/main/java/com/google/net/stubby/testing/integration/AbstractTransportTest.java
@@ -3,7 +3,6 @@
 import static com.google.net.stubby.testing.integration.Messages.PayloadType.COMPRESSABLE;
 import static com.google.net.stubby.testing.integration.Util.assertEquals;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 
 import com.google.common.base.Throwables;
@@ -41,8 +40,8 @@
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.Arrays;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
diff --git a/integration-testing/src/test/java/com/google/net/stubby/testing/integration/Http2OkHttpTest.java b/integration-testing/src/test/java/com/google/net/stubby/testing/integration/Http2OkHttpTest.java
index de8978d..c0230d9 100644
--- a/integration-testing/src/test/java/com/google/net/stubby/testing/integration/Http2OkHttpTest.java
+++ b/integration-testing/src/test/java/com/google/net/stubby/testing/integration/Http2OkHttpTest.java
@@ -1,7 +1,5 @@
 package com.google.net.stubby.testing.integration;
 
-import static org.junit.Assume.assumeTrue;
-
 import com.google.net.stubby.ChannelImpl;
 import com.google.net.stubby.transport.AbstractStream;
 import com.google.net.stubby.transport.netty.NettyServerBuilder;
@@ -35,10 +33,4 @@
   protected ChannelImpl createChannel() {
     return OkHttpChannelBuilder.forAddress("127.0.0.1", serverPort).build();
   }
-
-  @Override
-  public void clientStreaming() {
-    // TODO(user): Broken. We assume due to flow control bugs.
-    assumeTrue(false);
-  }
 }
diff --git a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientStream.java b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientStream.java
index 29b373c..3ca82ff 100644
--- a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientStream.java
+++ b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientStream.java
@@ -28,7 +28,8 @@
    */
   static OkHttpClientStream newStream(final Executor executor, ClientStreamListener listener,
                                        AsyncFrameWriter frameWriter,
-                                       OkHttpClientTransport transport) {
+                                       OkHttpClientTransport transport,
+                                       OutboundFlowController outboundFlow) {
     // Create a lock object that can be used by both the executor and methods in the stream
     // to ensure consistent locking behavior.
     final Object executorLock = new Object();
@@ -46,7 +47,7 @@
       }
     };
     return new OkHttpClientStream(synchronizingExecutor, listener, frameWriter, transport,
-        executorLock);
+        executorLock, outboundFlow);
   }
 
   @GuardedBy("executorLock")
@@ -54,15 +55,18 @@
   @GuardedBy("executorLock")
   private int processedWindow = OkHttpClientTransport.DEFAULT_INITIAL_WINDOW_SIZE;
   private final AsyncFrameWriter frameWriter;
+  private final OutboundFlowController outboundFlow;
   private final OkHttpClientTransport transport;
   // Lock used to synchronize with work done on the executor.
   private final Object executorLock;
+  private Object outboundFlowState;
 
   private OkHttpClientStream(final Executor executor,
                      final ClientStreamListener listener,
                      AsyncFrameWriter frameWriter,
                      OkHttpClientTransport transport,
-                     Object executorLock) {
+                     Object executorLock,
+                     OutboundFlowController outboundFlow) {
     super(listener, null, executor);
     if (!GRPC_V2_PROTOCOL) {
       throw new RuntimeException("okhttp transport can only work with V2 protocol!");
@@ -70,6 +74,7 @@
     this.frameWriter = frameWriter;
     this.transport = transport;
     this.executorLock = executorLock;
+    this.outboundFlow = outboundFlow;
   }
 
   public void transportHeadersReceived(List<Header> headers, boolean endOfStream) {
@@ -105,8 +110,7 @@
     // Per http2 SPEC, the max data length should be larger than 64K, while our frame size is
     // only 4K.
     Preconditions.checkState(buffer.size() < frameWriter.maxDataLength());
-    frameWriter.data(endOfStream, id(), buffer, (int) buffer.size());
-    frameWriter.flush();
+    outboundFlow.data(endOfStream, id(), buffer);
   }
 
   @Override
@@ -144,4 +148,12 @@
       transport.stopIfNecessary();
     }
   }
+
+  void setOutboundFlowState(Object outboundFlowState) {
+    this.outboundFlowState = outboundFlowState;
+  }
+
+  Object getOutboundFlowState() {
+    return outboundFlowState;
+  }
 }
diff --git a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientTransport.java b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientTransport.java
index be7bb27..d0a9050 100644
--- a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientTransport.java
+++ b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OkHttpClientTransport.java
@@ -82,6 +82,7 @@
   private final String defaultAuthority;
   private FrameReader frameReader;
   private AsyncFrameWriter frameWriter;
+  private OutboundFlowController outboundFlow;
   private final Object lock = new Object();
   @GuardedBy("lock")
   private int nextStreamId;
@@ -118,6 +119,7 @@
     this.executor = Preconditions.checkNotNull(executor);
     this.frameReader = Preconditions.checkNotNull(frameReader);
     this.frameWriter = Preconditions.checkNotNull(frameWriter);
+    this.outboundFlow = new OutboundFlowController(this, frameWriter);
     this.nextStreamId = nextStreamId;
   }
 
@@ -126,7 +128,7 @@
                                            Metadata.Headers headers,
                                            ClientStreamListener listener) {
     OkHttpClientStream clientStream = OkHttpClientStream.newStream(executor, listener,
-        frameWriter, this);
+        frameWriter, this, outboundFlow);
     if (goAway) {
       clientStream.setStatus(goAwayStatus, new Metadata.Trailers());
     } else {
@@ -154,6 +156,7 @@
       Variant variant = new Http20Draft14();
       frameReader = variant.newReader(source, true);
       frameWriter = new AsyncFrameWriter(variant.newWriter(sink, true), this, executor);
+      outboundFlow = new OutboundFlowController(this, frameWriter);
       frameWriter.connectionPreface();
       Settings settings = new Settings();
       frameWriter.settings(settings);
@@ -185,7 +188,6 @@
     return clientFrameHandler;
   }
 
-  @VisibleForTesting
   Map<Integer, OkHttpClientStream> getStreams() {
     return streams;
   }
@@ -395,8 +397,8 @@
     }
 
     @Override
-    public void windowUpdate(int arg0, long arg1) {
-      // TODO(user): outbound flow control.
+    public void windowUpdate(int streamId, long delta) {
+      outboundFlow.windowUpdate(streamId, (int) delta);
     }
 
     @Override
diff --git a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OutboundFlowController.java b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OutboundFlowController.java
new file mode 100644
index 0000000..a1881d0
--- /dev/null
+++ b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/OutboundFlowController.java
@@ -0,0 +1,399 @@
+package com.google.net.stubby.transport.okhttp;
+
+import static com.google.net.stubby.transport.okhttp.Utils.CONNECTION_STREAM_ID;
+import static com.google.net.stubby.transport.okhttp.Utils.DEFAULT_WINDOW_SIZE;
+import static com.google.net.stubby.transport.okhttp.Utils.MAX_FRAME_SIZE;
+import static java.lang.Math.ceil;
+import static java.lang.Math.max;
+import static java.lang.Math.min;
+
+import com.google.common.base.Preconditions;
+
+import com.squareup.okhttp.internal.spdy.FrameWriter;
+
+import okio.Buffer;
+
+import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.Queue;
+
+/**
+ * Simple outbound flow controller that evenly splits the connection window across all existing
+ * streams.
+ */
+class OutboundFlowController {
+  private static final OkHttpClientStream[] EMPTY_STREAM_ARRAY = new OkHttpClientStream[0];
+  private final OkHttpClientTransport transport;
+  private final FrameWriter frameWriter;
+  private int initialWindowSize = DEFAULT_WINDOW_SIZE;
+  private final OutboundFlowState connectionState = new OutboundFlowState(CONNECTION_STREAM_ID);
+
+  OutboundFlowController(OkHttpClientTransport transport, FrameWriter frameWriter) {
+    this.transport = Preconditions.checkNotNull(transport, "transport");
+    this.frameWriter = Preconditions.checkNotNull(frameWriter, "frameWriter");
+  }
+
+  synchronized void initialOutboundWindowSize(int newWindowSize) {
+    if (newWindowSize < 0) {
+      throw new IllegalArgumentException("Invalid initial window size: " + newWindowSize);
+    }
+
+    int delta = newWindowSize - initialWindowSize;
+    initialWindowSize = newWindowSize;
+    for (OkHttpClientStream stream : getActiveStreams()) {
+      // Verify that the maximum value is not exceeded by this change.
+      OutboundFlowState state = state(stream);
+      state.incrementStreamWindow(delta);
+    }
+
+    if (delta > 0) {
+      // The window size increased, send any pending frames for all streams.
+      writeStreams();
+    }
+  }
+
+  synchronized void windowUpdate(int streamId, int delta) {
+    if (streamId == CONNECTION_STREAM_ID) {
+      // Update the connection window and write any pending frames for all streams.
+      connectionState.incrementStreamWindow(delta);
+      writeStreams();
+    } else {
+      // Update the stream window and write any pending frames for the stream.
+      OutboundFlowState state = stateOrFail(streamId);
+      state.incrementStreamWindow(delta);
+
+      WriteStatus writeStatus = new WriteStatus();
+      state.writeBytes(state.writableWindow(), writeStatus);
+      if (writeStatus.hasWritten()) {
+        flush();
+      }
+    }
+  }
+
+  synchronized void data(boolean outFinished, int streamId, Buffer source) {
+    Preconditions.checkNotNull(source, "source");
+    if (streamId <= 0) {
+      throw new IllegalArgumentException("streamId must be > 0");
+    }
+
+    OutboundFlowState state = stateOrFail(streamId);
+    int window = state.writableWindow();
+    boolean framesAlreadyQueued = state.hasFrame();
+
+    OutboundFlowState.Frame frame = state.newFrame(source, outFinished);
+    if (!framesAlreadyQueued && window >= frame.size()) {
+      // Window size is large enough to send entire data frame
+      frame.write();
+      flush();
+      return;
+    }
+
+    // Enqueue the frame to be written when the window size permits.
+    frame.enqueue();
+
+    if (framesAlreadyQueued || window <= 0) {
+      // Stream already has frames pending or is stalled, don't send anything now.
+      return;
+    }
+
+    // Create and send a partial frame up to the window size.
+    frame.split(window).write();
+    flush();
+  }
+
+  private void flush() {
+    try {
+      frameWriter.flush();
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  private OutboundFlowState state(OkHttpClientStream stream) {
+    OutboundFlowState state = (OutboundFlowState) stream.getOutboundFlowState();
+    if (state == null) {
+      state = new OutboundFlowState(stream.id());
+      stream.setOutboundFlowState(state);
+    }
+    return state;
+  }
+
+  private OutboundFlowState state(int streamId) {
+    OkHttpClientStream stream = transport.getStreams().get(streamId);
+    return stream != null ? state(stream) : null;
+  }
+
+  private OutboundFlowState stateOrFail(int streamId) {
+    OutboundFlowState state = state(streamId);
+    if (state == null) {
+      throw new RuntimeException("Missing flow control window for stream: " + streamId);
+    }
+    return state;
+  }
+
+  /**
+   * Gets all active streams as an array.
+   */
+  private OkHttpClientStream[] getActiveStreams() {
+    return transport.getStreams().values().toArray(EMPTY_STREAM_ARRAY);
+  }
+
+  /**
+   * Writes as much data for all the streams as possible given the current flow control windows.
+   */
+  private void writeStreams() {
+    OkHttpClientStream[] streams = getActiveStreams();
+    int connectionWindow = connectionState.window();
+    for (int numStreams = streams.length; numStreams > 0 && connectionWindow > 0;) {
+      int nextNumStreams = 0;
+      int windowSlice = (int) ceil(connectionWindow / (float) numStreams);
+      for (int index = 0; index < numStreams && connectionWindow > 0; ++index) {
+        OkHttpClientStream stream = streams[index];
+        OutboundFlowState state = state(stream);
+
+        int bytesForStream = min(connectionWindow, min(state.unallocatedBytes(), windowSlice));
+        if (bytesForStream > 0) {
+          state.allocateBytes(bytesForStream);
+          connectionWindow -= bytesForStream;
+        }
+
+        if (state.unallocatedBytes() > 0) {
+          // There is more data to process for this stream. Add it to the next
+          // pass.
+          streams[nextNumStreams++] = stream;
+        }
+      }
+      numStreams = nextNumStreams;
+    }
+
+    // Now take one last pass through all of the streams and write any allocated bytes.
+    WriteStatus writeStatus = new WriteStatus();
+    for (OkHttpClientStream stream : getActiveStreams()) {
+      OutboundFlowState state = state(stream);
+      state.writeBytes(state.allocatedBytes(), writeStatus);
+      state.clearAllocatedBytes();
+    }
+
+    if (writeStatus.hasWritten()) {
+      flush();
+    }
+  }
+
+  /**
+   * Simple status that keeps track of the number of writes performed.
+   */
+  private final class WriteStatus {
+    int numWrites;
+
+    void incrementNumWrites() {
+      numWrites++;
+    }
+
+    boolean hasWritten() {
+      return numWrites > 0;
+    }
+  }
+
+  /**
+   * The outbound flow control state for a single stream.
+   */
+  private final class OutboundFlowState {
+    final Queue<Frame> pendingWriteQueue;
+    final int streamId;
+    int queuedBytes;
+    int window = initialWindowSize;
+    int allocatedBytes;
+
+    OutboundFlowState(int streamId) {
+      this.streamId = streamId;
+      pendingWriteQueue = new ArrayDeque<Frame>(2);
+    }
+
+    int window() {
+      return window;
+    }
+
+    void allocateBytes(int bytes) {
+      allocatedBytes += bytes;
+    }
+
+    int allocatedBytes() {
+      return allocatedBytes;
+    }
+
+    int unallocatedBytes() {
+      return streamableBytes() - allocatedBytes;
+    }
+
+    void clearAllocatedBytes() {
+      allocatedBytes = 0;
+    }
+
+    /**
+     * Increments the flow control window for this stream by the given delta and returns the new
+     * value.
+     */
+    int incrementStreamWindow(int delta) {
+      if (delta > 0 && Integer.MAX_VALUE - delta < window) {
+        throw new IllegalArgumentException("Window size overflow for stream: " + streamId);
+      }
+      window += delta;
+
+      return window;
+    }
+
+    /**
+     * Returns the maximum writable window (minimum of the stream and connection windows).
+     */
+    int writableWindow() {
+      return min(window, connectionState.window());
+    }
+
+    int streamableBytes() {
+      return max(0, min(window, queuedBytes));
+    }
+
+    /**
+     * Creates a new frame with the given values but does not add it to the pending queue.
+     */
+    Frame newFrame(Buffer data, boolean endStream) {
+      return new Frame(data, endStream);
+    }
+
+    /**
+     * Indicates whether or not there are frames in the pending queue.
+     */
+    boolean hasFrame() {
+      return !pendingWriteQueue.isEmpty();
+    }
+
+    /**
+     * Returns the the head of the pending queue, or {@code null} if empty.
+     */
+    private Frame peek() {
+      return pendingWriteQueue.peek();
+    }
+
+    /**
+     * Writes up to the number of bytes from the pending queue.
+     */
+    int writeBytes(int bytes, WriteStatus writeStatus) {
+      int bytesAttempted = 0;
+      int maxBytes = min(bytes, writableWindow());
+      while (hasFrame()) {
+        Frame pendingWrite = peek();
+        if (maxBytes >= pendingWrite.size()) {
+          // Window size is large enough to send entire data frame
+          writeStatus.incrementNumWrites();
+          bytesAttempted += pendingWrite.size();
+          pendingWrite.write();
+        } else if (maxBytes <= 0) {
+          // No data from the current frame can be written - we're done.
+          // We purposely check this after first testing the size of the
+          // pending frame to properly handle zero-length frame.
+          break;
+        } else {
+          // We can send a partial frame
+          Frame partialFrame = pendingWrite.split(maxBytes);
+          writeStatus.incrementNumWrites();
+          bytesAttempted += partialFrame.size();
+          partialFrame.write();
+        }
+
+        // Update the threshold.
+        maxBytes = min(bytes - bytesAttempted, writableWindow());
+      }
+      return bytesAttempted;
+    }
+
+    /**
+     * A wrapper class around the content of a data frame.
+     */
+    private final class Frame {
+      final Buffer data;
+      final boolean endStream;
+      boolean enqueued;
+
+      Frame(Buffer data, boolean endStream) {
+        this.data = data;
+        this.endStream = endStream;
+      }
+
+      /**
+       * Gets the total size (in bytes) of this frame including the data and padding.
+       */
+      int size() {
+        return (int) data.size();
+      }
+
+      void enqueue() {
+        if (!enqueued) {
+          enqueued = true;
+          pendingWriteQueue.offer(this);
+
+          // Increment the number of pending bytes for this stream.
+          queuedBytes += size();
+        }
+      }
+
+      /**
+       * Writes the frame and decrements the stream and connection window sizes. If the frame is in
+       * the pending queue, the written bytes are removed from this branch of the priority tree.
+       */
+      void write() {
+        // Using a do/while loop because if the buffer is empty we still need to call
+        // the writer once to send the empty frame.
+        do {
+          int bytesToWrite = size();
+          int frameBytes = min(bytesToWrite, MAX_FRAME_SIZE);
+          if (frameBytes == bytesToWrite) {
+            // All the bytes fit into a single HTTP/2 frame, just send it all.
+            connectionState.incrementStreamWindow(-bytesToWrite);
+            incrementStreamWindow(-bytesToWrite);
+            try {
+              frameWriter.data(endStream, streamId, data, bytesToWrite);
+            } catch (IOException e) {
+              throw new RuntimeException(e);
+            }
+            if (enqueued) {
+              // It's enqueued - remove it from the head of the pending write queue.
+              queuedBytes -= bytesToWrite;
+              pendingWriteQueue.remove(this);
+            }
+            return;
+          }
+
+          // Split a chunk that will fit into a single HTTP/2 frame and write it.
+          Frame frame = split(frameBytes);
+          frame.write();
+        } while (size() > 0);
+      }
+
+      /**
+       * Creates a new frame that is a view of this frame's data. The {@code maxBytes} are first
+       * split from the data buffer. If not all the requested bytes are available, the remaining
+       * bytes are then split from the padding (if available).
+       *
+       * @param maxBytes the maximum number of bytes that is allowed in the created frame.
+       * @return the partial frame.
+       */
+      Frame split(int maxBytes) {
+        // The requested maxBytes should always be less than the size of this frame.
+        assert maxBytes < size() : "Attempting to split a frame for the full size.";
+
+        // Get the portion of the data buffer to be split. Limit to the readable bytes.
+        int dataSplit = min(maxBytes, (int) data.size());
+
+        Buffer splitSlice = new Buffer();
+        splitSlice.write(data, dataSplit);
+
+        Frame frame = new Frame(splitSlice, false);
+
+        if (enqueued) {
+          queuedBytes -= dataSplit;
+        }
+        return frame;
+      }
+    }
+  }
+}
diff --git a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/Utils.java b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/Utils.java
index 7293b97..6a42970 100644
--- a/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/Utils.java
+++ b/okhttp/src/main/java/com/google/net/stubby/transport/okhttp/Utils.java
@@ -10,6 +10,10 @@
  * Common utility methods for OkHttp transport.
  */
 class Utils {
+  static final int DEFAULT_WINDOW_SIZE = 65535;
+  static final int CONNECTION_STREAM_ID = 0;
+  static final int MAX_FRAME_SIZE = 16384;
+
   public static Metadata.Headers convertHeaders(List<Header> http2Headers) {
     return new Metadata.Headers(convertHeadersToArray(http2Headers));
   }