diff --git a/akka-stream/src/main/scala/akka/stream/impl2/ActorBasedFlowMaterializer.scala b/akka-stream/src/main/scala/akka/stream/impl2/ActorBasedFlowMaterializer.scala
index 8b07ce5dea..962d94d3a1 100644
--- a/akka-stream/src/main/scala/akka/stream/impl2/ActorBasedFlowMaterializer.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl2/ActorBasedFlowMaterializer.scala
@@ -20,6 +20,7 @@ import akka.stream.impl.ConflateImpl
 import akka.stream.impl.ExpandImpl
 import akka.stream.impl.BufferImpl
 import akka.stream.impl.FanoutProcessorImpl
+import akka.stream.impl.BlackholeSubscriber
 
 /**
  * INTERNAL API
@@ -61,6 +62,18 @@ private[akka] object Ast {
     override def name = "buffer"
   }
 
+  sealed trait FanAstNode {
+    def name: String
+  }
+
+  case object Merge extends FanAstNode {
+    override def name = "merge"
+  }
+
+  case object Broadcast extends FanAstNode {
+    override def name = "broadcast"
+  }
+
 }
 
 /**
@@ -170,6 +183,23 @@ case class ActorBasedFlowMaterializer(override val settings: MaterializerSetting
       throw new IllegalStateException(s"Stream supervisor must be a local actor, was [${supervisor.getClass.getName}]")
   }
 
+  override def materializeFan[In, Out](op: Ast.FanAstNode, inputCount: Int, outputCount: Int): (immutable.Seq[Subscriber[In]], immutable.Seq[Publisher[Out]]) = op match {
+    case Ast.Merge ⇒
+      // FIXME real impl
+      require(outputCount == 1)
+      (Vector.fill(inputCount)(dummySubscriber[In]), List(dummyPublisher[Out]))
+    case Ast.Broadcast ⇒
+      // FIXME real impl
+      require(inputCount == 1)
+      (List(dummySubscriber[In]), Vector.fill(outputCount)(dummyPublisher[Out]))
+  }
+
+  // FIXME remove
+  private def dummySubscriber[T]: Subscriber[T] = new BlackholeSubscriber[T](1)
+  private def dummyPublisher[T]: Publisher[T] = new Publisher[T] {
+    def subscribe(subscriber: Subscriber[_ >: T]): Unit = subscriber.onComplete()
+  }
+
 }
 
 /**
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowGraph.scala b/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowGraph.scala
index 97ae52210e..4bb2bd7e36 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowGraph.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowGraph.scala
@@ -10,7 +10,7 @@ import scalax.collection.immutable.{ Graph ⇒ ImmutableGraph }
 import org.reactivestreams.Subscriber
 import akka.stream.impl.BlackholeSubscriber
 import org.reactivestreams.Publisher
-import org.reactivestreams.Processor
+import akka.stream.impl2.Ast
 
 /**
  * Fan-in and fan-out vertices in the [[FlowGraph]] implements
@@ -376,17 +376,12 @@ class FlowGraph private[akka] (private[akka] val graph: ImmutableGraph[FlowGraph
   def run()(implicit materializer: FlowMaterializer): MaterializedFlowGraph = {
     import scalax.collection.GraphTraversal._
 
-    // FIXME remove when real materialization is done
-    def dummyProcessor(name: String): Processor[Any, Any] = new BlackholeSubscriber[Any](1) with Publisher[Any] with Processor[Any, Any] {
-      def subscribe(subscriber: Subscriber[_ >: Any]): Unit = subscriber.onComplete()
-      override def toString = name
-    }
-
     // start with sinks
     val startingNodes = graph.nodes.filter(n ⇒ n.isLeaf && n.diSuccessors.isEmpty)
 
     case class Memo(visited: Set[graph.EdgeT] = Set.empty,
-                    nodeProcessor: Map[graph.NodeT, Processor[Any, Any]] = Map.empty,
+                    downstreamSubscriber: Map[graph.EdgeT, Subscriber[Any]] = Map.empty,
+                    upstreamPublishers: Map[graph.EdgeT, Publisher[Any]] = Map.empty,
                     sources: Map[Source[_], FlowWithSink[Any, Any]] = Map.empty,
                     materializedSinks: Map[Sink[_], Any] = Map.empty)
 
@@ -403,8 +398,8 @@ class FlowGraph private[akka] (private[akka] val graph: ImmutableGraph[FlowGraph
               val flow = edge.label.asInstanceOf[ProcessorFlow[Any, Any]]
 
               // returns the materialized sink, if any
-              def connectProcessorToDownstream(processor: Processor[Any, Any]): Option[(SinkWithKey[_, _], Any)] = {
-                val f = flow.withSource(PublisherSource(processor))
+              def connectToDownstream(publisher: Publisher[Any]): Option[(SinkWithKey[_, _], Any)] = {
+                val f = flow.withSource(PublisherSource(publisher))
                 edge.to.value match {
                   case SinkVertex(sink: SinkWithKey[_, _]) ⇒
                     val mf = f.withSink(sink.asInstanceOf[Sink[Any]]).run()
@@ -413,36 +408,55 @@ class FlowGraph private[akka] (private[akka] val graph: ImmutableGraph[FlowGraph
                     f.withSink(sink.asInstanceOf[Sink[Any]]).run()
                     None
                   case _ ⇒
-                    f.withSink(SubscriberSink(memo.nodeProcessor(edge.to))).run()
+                    f.withSink(SubscriberSink(memo.downstreamSubscriber(edge))).run()
                     None
                 }
               }
 
               edge.from.value match {
                 case SourceVertex(src) ⇒
-                  val f = flow.withSink(SubscriberSink(memo.nodeProcessor(edge.to)))
+                  val f = flow.withSink(SubscriberSink(memo.downstreamSubscriber(edge)))
                   // connect the source with the flow later
                   memo.copy(visited = memo.visited + edge,
                     sources = memo.sources.updated(src, f))
 
-                case _: FanOperation[_] ⇒
-                  val processor = edge.from.value match {
-                    case merge: Merge[_] ⇒
-                      // FIXME materialize Merge
-                      dummyProcessor("merge-processor")
-                    case bcast: Broadcast[_] ⇒
-                      memo.nodeProcessor.getOrElse(edge.from, {
-                        // FIXME materialize Broadcast
-                        dummyProcessor("bcast-processor")
-                      })
-                    case other ⇒
-                      throw new IllegalArgumentException("Unknown fan operation: " + other)
-                  }
-                  val materializedSink = connectProcessorToDownstream(processor)
+                case merge: Merge[_] ⇒
+                  // one subscriber for each incoming edge of the merge vertex
+                  val (subscribers, publishers) =
+                    materializer.materializeFan[Any, Any](Ast.Merge, edge.from.inDegree, 1)
+                  val publisher = publishers.head
+                  val edgeSubscribers = edge.from.incoming.zip(subscribers)
+                  val materializedSink = connectToDownstream(publisher)
                   memo.copy(
                     visited = memo.visited + edge,
-                    nodeProcessor = memo.nodeProcessor.updated(edge.from, processor),
+                    downstreamSubscriber = memo.downstreamSubscriber ++ edgeSubscribers,
                     materializedSinks = memo.materializedSinks ++ materializedSink)
+
+                case bcast: Broadcast[_] ⇒
+                  if (memo.upstreamPublishers.contains(edge)) {
+                    // broadcast vertex already materialized
+                    val materializedSink = connectToDownstream(memo.upstreamPublishers(edge))
+                    memo.copy(
+                      visited = memo.visited + edge,
+                      materializedSinks = memo.materializedSinks ++ materializedSink)
+                  } else {
+                    // one publisher for each outgoing edge of the broadcast vertex   
+                    val (subscribers, publishers) =
+                      materializer.materializeFan[Any, Any](Ast.Broadcast, 1, edge.from.outDegree)
+                    val subscriber = subscribers.head
+                    val edgePublishers = edge.from.outgoing.zip(publishers).toMap
+                    val publisher = edgePublishers(edge)
+                    val materializedSink = connectToDownstream(publisher)
+                    memo.copy(
+                      visited = memo.visited + edge,
+                      downstreamSubscriber = memo.downstreamSubscriber + (edge.from.incoming.head -> subscriber),
+                      upstreamPublishers = memo.upstreamPublishers ++ edgePublishers,
+                      materializedSinks = memo.materializedSinks ++ materializedSink)
+                  }
+
+                case other ⇒
+                  throw new IllegalArgumentException("Unknown fan operation: " + other)
+
               }
             }
 
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowMaterializer.scala b/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowMaterializer.scala
index f444f0ed94..ca2a3ee6d1 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowMaterializer.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl2/FlowMaterializer.scala
@@ -3,9 +3,12 @@
  */
 package akka.stream.scaladsl2
 
+import scala.collection.immutable
 import akka.actor.{ ActorContext, ActorRefFactory, ActorSystem, ExtendedActorSystem }
 import akka.stream.MaterializerSettings
 import akka.stream.impl2.{ ActorBasedFlowMaterializer, Ast, FlowNameCounter, StreamSupervisor }
+import org.reactivestreams.Subscriber
+import org.reactivestreams.Publisher
 
 object FlowMaterializer {
 
@@ -137,6 +140,11 @@ abstract class FlowMaterializer(val settings: MaterializerSettings) {
    */
   def materialize[In, Out](source: Source[In], sink: Sink[Out], ops: List[Ast.AstNode]): MaterializedFlow
 
+  /**
+   * Create publishers and subscribers for fan-in and fan-out operations.
+   */
+  def materializeFan[In, Out](op: Ast.FanAstNode, inputCount: Int, outputCount: Int): (immutable.Seq[Subscriber[In]], immutable.Seq[Publisher[Out]])
+
 }
 
 /**
diff --git a/akka-stream/src/test/scala/akka/stream/scaladsl2/FlowGraphCompileSpec.scala b/akka-stream/src/test/scala/akka/stream/scaladsl2/FlowGraphCompileSpec.scala
index dd6ca709a3..b6e2192d56 100644
--- a/akka-stream/src/test/scala/akka/stream/scaladsl2/FlowGraphCompileSpec.scala
+++ b/akka-stream/src/test/scala/akka/stream/scaladsl2/FlowGraphCompileSpec.scala
@@ -36,7 +36,7 @@ class FlowGraphCompileSpec extends AkkaSpec {
           addEdge(in1, f1, merge).
           addEdge(in2, f2, merge).
           addEdge(merge, f3, out1)
-      }
+      }.run()
     }
 
     "build simple broadcast" in {
@@ -46,7 +46,7 @@ class FlowGraphCompileSpec extends AkkaSpec {
           addEdge(in1, f1, bcast).
           addEdge(bcast, f2, out1).
           addEdge(bcast, f3, out2)
-      }
+      }.run()
     }
 
     "build simple merge - broadcast" in {
@@ -59,7 +59,7 @@ class FlowGraphCompileSpec extends AkkaSpec {
           addEdge(merge, f3, bcast).
           addEdge(bcast, f4, out1).
           addEdge(bcast, f5, out2)
-      }
+      }.run()
     }
 
     "build simple merge - broadcast with implicits" in {
@@ -70,7 +70,7 @@ class FlowGraphCompileSpec extends AkkaSpec {
         in1 ~> f1 ~> merge ~> f2 ~> bcast ~> f3 ~> out1
         in2 ~> f4 ~> merge
         bcast ~> f5 ~> out2
-      }
+      }.run()
     }
 
     /**
@@ -161,7 +161,7 @@ class FlowGraphCompileSpec extends AkkaSpec {
       FlowGraph(partial2) { implicit b ⇒
         b.attachSink(undefinedSink1, out1)
         b.attachSink(UndefinedSink[String]("sink2"), out2)
-      }
+      }.run()
     }
 
   }