diff --git a/comm.go b/comm.go
index 430e6a6..182e992 100644
--- a/comm.go
+++ b/comm.go
@@ -104,3 +104,21 @@ func rpcWithSubs(subs ...*pb.RPC_SubOpts) *RPC {
 func rpcWithMessages(msgs ...*pb.Message) *RPC {
 	return &RPC{RPC: pb.RPC{Publish: msgs}}
 }
+
+func rpcWithControl(msgs []*pb.Message,
+	ihave []*pb.ControlIHave,
+	iwant []*pb.ControlIWant,
+	graft []*pb.ControlGraft,
+	prune []*pb.ControlPrune) *RPC {
+	return &RPC{
+		RPC: pb.RPC{
+			Publish: msgs,
+			Control: &pb.ControlMessage{
+				Ihave: ihave,
+				Iwant: iwant,
+				Graft: graft,
+				Prune: prune,
+			},
+		},
+	}
+}
diff --git a/gossipsub.go b/gossipsub.go
index 0d63f92..2ecbb0a 100644
--- a/gossipsub.go
+++ b/gossipsub.go
@@ -62,7 +62,121 @@ func (gs *GossipSubRouter) RemovePeer(p peer.ID) {
 }
 
 func (gs *GossipSubRouter) HandleRPC(rpc *RPC) {
-	// TODO
+	ctl := rpc.GetControl()
+	if ctl == nil {
+		return
+	}
+
+	iwant := gs.handleIHave(ctl)
+	msgs := gs.handleIWant(ctl)
+	prune := gs.handleGraft(rpc.from, ctl)
+	gs.handlePrune(rpc.from, ctl)
+
+	if len(iwant) == 0 && len(msgs) == 0 && len(prune) == 0 {
+		return
+	}
+
+	// TODO piggyback gossip IHAVE
+	out := rpcWithControl(msgs, nil, iwant, nil, prune)
+
+	mch, ok := gs.p.peers[rpc.from]
+	if !ok {
+		return
+	}
+
+	select {
+	case mch <- out:
+	default:
+		// TODO PRUNE messages should be reliable; schedule for piggybacking or retry
+		log.Infof("dropping message to peer %s: queue full", rpc.from)
+	}
+}
+
+func (gs *GossipSubRouter) handleIHave(ctl *pb.ControlMessage) []*pb.ControlIWant {
+	iwant := make(map[string]struct{})
+
+	for _, ihave := range ctl.GetIhave() {
+		topic := ihave.GetTopicID()
+		_, ok := gs.mesh[topic]
+		if !ok {
+			continue
+		}
+
+		for _, mid := range ihave.GetMessageIDs() {
+			if gs.p.seenMessage(mid) {
+				continue
+			}
+			iwant[mid] = struct{}{}
+		}
+	}
+
+	if len(iwant) == 0 {
+		return nil
+	}
+
+	iwantlst := make([]string, 0, len(iwant))
+	for mid := range iwant {
+		iwantlst = append(iwantlst, mid)
+	}
+
+	return []*pb.ControlIWant{&pb.ControlIWant{MessageIDs: iwantlst}}
+}
+
+func (gs *GossipSubRouter) handleIWant(ctl *pb.ControlMessage) []*pb.Message {
+	ihave := make(map[string]*pb.Message)
+	for _, iwant := range ctl.GetIwant() {
+		for _, mid := range iwant.GetMessageIDs() {
+			msg, ok := gs.mcache.Get(mid)
+			if ok {
+				ihave[mid] = msg
+			}
+		}
+	}
+
+	if len(ihave) == 0 {
+		return nil
+	}
+
+	msgs := make([]*pb.Message, 0, len(ihave))
+	for _, msg := range ihave {
+		msgs = append(msgs, msg)
+	}
+
+	return msgs
+}
+
+func (gs *GossipSubRouter) handleGraft(p peer.ID, ctl *pb.ControlMessage) []*pb.ControlPrune {
+	var prune []string
+	for _, graft := range ctl.GetGraft() {
+		topic := graft.GetTopicID()
+		peers, ok := gs.mesh[topic]
+		if !ok {
+			prune = append(prune, topic)
+		} else {
+			peers[p] = struct{}{}
+		}
+	}
+
+	if len(prune) == 0 {
+		return nil
+	}
+
+	cprune := make([]*pb.ControlPrune, 0, len(prune))
+	for _, topic := range prune {
+		cprune = append(cprune, &pb.ControlPrune{TopicID: &topic})
+	}
+
+	return cprune
+}
+
+func (gs *GossipSubRouter) handlePrune(p peer.ID, ctl *pb.ControlMessage) {
+	for _, prune := range ctl.GetPrune() {
+		topic := prune.GetTopicID()
+		peers, ok := gs.mesh[topic]
+		if ok {
+			delete(peers, p)
+		}
+	}
 }
 
 func (gs *GossipSubRouter) Publish(from peer.ID, msg *pb.Message) {
diff --git a/mcache.go b/mcache.go
index 47e869e..01d78f6 100644
--- a/mcache.go
+++ b/mcache.go
@@ -14,3 +14,8 @@ type MessageCache struct {
 func (mc *MessageCache) Add(msg *pb.Message) {
 	// TODO
 }
+
+func (mc *MessageCache) Get(mid string) (*pb.Message, bool) {
+	// TODO
+	return nil, false
+}