diff --git a/core/api/src/main/java/org/onlab/onos/net/topology/TopologyEvent.java b/core/api/src/main/java/org/onlab/onos/net/topology/TopologyEvent.java
index 0be5323..268b6ac 100644
--- a/core/api/src/main/java/org/onlab/onos/net/topology/TopologyEvent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/topology/TopologyEvent.java
@@ -1,12 +1,17 @@
 package org.onlab.onos.net.topology;
 
 import org.onlab.onos.event.AbstractEvent;
+import org.onlab.onos.event.Event;
+
+import java.util.List;
 
 /**
  * Describes network topology event.
  */
 public class TopologyEvent extends AbstractEvent<TopologyEvent.Type, Topology> {
 
+    private final List<Event> reasons;
+
     /**
      * Type of topology events.
      */
@@ -23,9 +28,11 @@
      *
      * @param type     topology event type
      * @param topology event topology subject
+     * @param reasons  list of events that triggered topology change
      */
-    public TopologyEvent(Type type, Topology topology) {
+    public TopologyEvent(Type type, Topology topology, List<Event> reasons) {
         super(type, topology);
+        this.reasons = reasons;
     }
 
     /**
@@ -33,10 +40,24 @@
      *
      * @param type     link event type
      * @param topology event topology subject
+     * @param reasons  list of events that triggered topology change
      * @param time     occurrence time
      */
-    public TopologyEvent(Type type, Topology topology, long time) {
+    public TopologyEvent(Type type, Topology topology, List<Event> reasons,
+                         long time) {
         super(type, topology, time);
+        this.reasons = reasons;
+    }
+
+
+    /**
+     * Returns the list of events that triggered the topology change.
+     *
+     * @return list of events responsible for change in topology; null if
+     * initial topology computation
+     */
+    public List<Event> reasons() {
+        return reasons;
     }
 
 }