diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/AdjacencyListWritable.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/AdjacencyListWritable.java
new file mode 100644
index 0000000..b07017a
--- /dev/null
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/AdjacencyListWritable.java
@@ -0,0 +1,108 @@
+/*
+ * Copyright 2009-2010 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.uci.ics.pregelix.example.maximalclique;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Set;
+import java.util.TreeSet;
+
+import org.apache.hadoop.io.Writable;
+
+import edu.uci.ics.pregelix.example.io.VLongWritable;
+
+/**
+ * The adjacency list is the value part of the mapper output
+ */
+public class AdjacencyListWritable implements Writable {
+
+    private VLongWritable sourceVertex = new VLongWritable();
+    private Set<VLongWritable> destinationVertexes = new TreeSet<VLongWritable>();
+
+    public AdjacencyListWritable() {
+    }
+
+    public void reset() {
+        this.destinationVertexes.clear();
+    }
+
+    public void setSource(VLongWritable source) {
+        this.sourceVertex = source;
+    }
+
+    public void addNeighbor(VLongWritable neighbor) {
+        destinationVertexes.add(neighbor);
+    }
+
+    @Override
+    public void readFields(DataInput input) throws IOException {
+        sourceVertex = new VLongWritable();
+        destinationVertexes.clear();
+        sourceVertex.readFields(input);
+        int numberOfNeighbors = input.readInt();
+        for (int i = 0; i < numberOfNeighbors; i++) {
+            VLongWritable neighbor = new VLongWritable();
+            neighbor.readFields(input);
+            destinationVertexes.add(neighbor);
+        }
+    }
+
+    @Override
+    public void write(DataOutput output) throws IOException {
+        sourceVertex.write(output);
+        output.writeInt(destinationVertexes.size());
+        for (VLongWritable dest : destinationVertexes) {
+            dest.write(output);
+        }
+    }
+
+    public AdjacencyListWritable clone() {
+        AdjacencyListWritable clone = new AdjacencyListWritable();
+        clone.setSource(sourceVertex);
+        for (VLongWritable dest : destinationVertexes) {
+            clone.addNeighbor(dest);
+        }
+        return clone;
+    }
+
+    public int numberOfNeighbors() {
+        return destinationVertexes.size();
+    }
+
+    public void removeNeighbor(VLongWritable v) {
+        destinationVertexes.remove(v);
+    }
+
+    public VLongWritable getSource() {
+        return sourceVertex;
+    }
+
+    public Iterator<VLongWritable> getNeighbors() {
+        return destinationVertexes.iterator();
+    }
+
+    public void cleanNonMatch(Collection<VLongWritable> matches) {
+        destinationVertexes.retainAll(matches);
+    }
+
+    public boolean isNeighbor(VLongWritable v) {
+        return destinationVertexes.contains(v);
+    }
+
+}
diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/CliquesWritable.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/CliquesWritable.java
new file mode 100644
index 0000000..940fe2b
--- /dev/null
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/CliquesWritable.java
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2009-2010 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.uci.ics.pregelix.example.maximalclique;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.hadoop.io.Writable;
+
+import edu.uci.ics.pregelix.example.io.VLongWritable;
+
+public class CliquesWritable implements Writable {
+
+    private List<VLongWritable> cliques = new ArrayList<VLongWritable>();
+    private int sizeOfClique = 0;
+
+    public CliquesWritable(List<VLongWritable> cliques, int sizeOfClique) {
+        this.cliques = cliques;
+        this.sizeOfClique = sizeOfClique;
+    }
+
+    public CliquesWritable() {
+
+    }
+
+    public void setClusterSize(int sizeOfClique) {
+        this.sizeOfClique = sizeOfClique;
+    }
+
+    public void setCliques(List<VLongWritable> cliques) {
+        this.cliques = cliques;
+    }
+
+    public int getSizeOfClique() {
+        return sizeOfClique;
+    }
+
+    public void reset() {
+        this.cliques.clear();
+        this.sizeOfClique = 0;
+    }
+
+    @Override
+    public void readFields(DataInput input) throws IOException {
+        cliques.clear();
+        int numCliques = input.readInt();
+        if (numCliques < 0) {
+            sizeOfClique = 0;
+            return;
+        }
+        sizeOfClique = input.readInt();
+        for (int i = 0; i < numCliques; i++) {
+            for (int j = 0; j < sizeOfClique; j++) {
+                VLongWritable vid = new VLongWritable();
+                vid.readFields(input);
+                cliques.add(vid);
+            }
+        }
+    }
+
+    @Override
+    public void write(DataOutput output) throws IOException {
+        if (sizeOfClique <= 0) {
+            output.writeInt(-1);
+            return;
+        }
+        output.writeInt(cliques.size() / sizeOfClique);
+        output.writeInt(sizeOfClique);
+
+        for (int i = 0; i < cliques.size(); i++) {
+            cliques.get(i).write(output);
+        }
+    }
+
+    @Override
+    public String toString() {
+        if (sizeOfClique == 0)
+            return "";
+        StringBuffer sb = new StringBuffer();
+        int numCliques = cliques.size() / sizeOfClique;
+        for (int i = 0; i < numCliques; i++) {
+            for (int j = 0; j < sizeOfClique - 1; j++) {
+                sb.append(cliques.get(j));
+                sb.append(",");
+            }
+            sb.append(cliques.get(sizeOfClique - 1));
+            sb.append(";");
+        }
+        return sb.toString();
+    }
+}
diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java
new file mode 100644
index 0000000..c128a92
--- /dev/null
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java
@@ -0,0 +1,255 @@
+/*
+ * Copyright 2009-2010 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.uci.ics.pregelix.example.maximalclique;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.BitSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+import org.apache.hadoop.io.NullWritable;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.mapreduce.RecordWriter;
+import org.apache.hadoop.mapreduce.TaskAttemptContext;
+
+import edu.uci.ics.pregelix.api.graph.Edge;
+import edu.uci.ics.pregelix.api.graph.Vertex;
+import edu.uci.ics.pregelix.api.io.VertexWriter;
+import edu.uci.ics.pregelix.api.io.text.TextVertexOutputFormat;
+import edu.uci.ics.pregelix.api.io.text.TextVertexOutputFormat.TextVertexWriter;
+import edu.uci.ics.pregelix.example.io.VLongWritable;
+
+public class MaximalCliqueVertex extends Vertex<VLongWritable, CliquesWritable, NullWritable, AdjacencyListWritable> {
+
+    private Map<VLongWritable, AdjacencyListWritable> map = new TreeMap<VLongWritable, AdjacencyListWritable>();
+    private List<VLongWritable> vertexList = new ArrayList<VLongWritable>();
+    private Map<VLongWritable, Integer> invertedMap = new TreeMap<VLongWritable, Integer>();
+    private int largestCliqueSizeSoFar = 0;
+    private List<BitSet> currentMaximalCliques = new ArrayList<BitSet>();
+    private CliquesWritable tmpValue = new CliquesWritable();
+    private List<VLongWritable> cliques = new ArrayList<VLongWritable>();
+
+    private void updateCurrentMaximalCliques(Iterator<AdjacencyListWritable> values) {
+        map.clear();
+        vertexList.clear();
+        invertedMap.clear();
+        currentMaximalCliques.clear();
+        cliques.clear();
+
+        // build the initial sub graph
+        while (values.hasNext()) {
+            AdjacencyListWritable adj = values.next();
+            map.put(adj.getSource(), adj);
+        }
+        VLongWritable srcId = getVertexId();
+        map.put(srcId, new AdjacencyListWritable());
+
+        // build the vertex list (vertex id in ascending order) and the inverted list of vertexes
+        int i = 0;
+        for (VLongWritable v : map.keySet()) {
+            vertexList.add(v);
+            invertedMap.put(v, i++);
+        }
+
+        //clean up adjacency list --- remove vertexes who are not neighbors of key
+        for (AdjacencyListWritable adj : map.values()) {
+            adj.cleanNonMatch(vertexList);
+        }
+
+        // get the h-index of the subgraph --- which is the maximum depth to explore
+        int[] neighborCounts = new int[map.size()];
+        i = 0;
+        for (AdjacencyListWritable adj : map.values()) {
+            neighborCounts[i++] = adj.numberOfNeighbors();
+        }
+        Arrays.sort(neighborCounts);
+        int h = 0;
+        for (i = neighborCounts.length - 1; i >= 0; i--) {
+            if (h >= neighborCounts[i]) {
+                break;
+            }
+            h++;
+        }
+        if (h < largestCliqueSizeSoFar) {
+            return;
+        }
+
+        //start depth-first search
+        BitSet cliqueSoFar = new BitSet(h);
+        for (VLongWritable v : vertexList) {
+            cliqueSoFar.set(invertedMap.get(v));
+            searchClique(h, cliqueSoFar, 1, v);
+            cliqueSoFar.clear();
+        }
+
+        //output local maximal cliques
+        for (BitSet clique : currentMaximalCliques) {
+            int keyIndex = invertedMap.get(srcId);
+            clique.set(keyIndex);
+            generateClique(clique);
+            tmpValue.setCliques(cliques);
+            tmpValue.setClusterSize(clique.cardinality());
+        }
+        
+        //update the vertex state
+        setVertexValue(tmpValue);
+    }
+
+    // output a clique with the bitmap representation
+    private void generateClique(BitSet clique) {
+        for (int j = 0; j < clique.length();) {
+            j = clique.nextSetBit(j);
+            VLongWritable v = vertexList.get(j);
+            cliques.add(v);
+            j++;
+        }
+    }
+
+    private void searchClique(int maxDepth, BitSet cliqueSoFar, int depthSoFar, VLongWritable currentSource) {
+        if (depthSoFar > maxDepth) {
+            // update maximal clique info
+            updateMaximalClique(cliqueSoFar);
+            return;
+        }
+
+        AdjacencyListWritable adj = map.get(currentSource);
+        Iterator<VLongWritable> neighbors = adj.getNeighbors();
+        ++depthSoFar;
+        while (neighbors.hasNext()) {
+            VLongWritable neighbor = neighbors.next();
+            if (!isTested(neighbor, cliqueSoFar) && isClique(neighbor, cliqueSoFar)) {
+                //snapshot the clique
+                int cliqueLength = cliqueSoFar.length();
+                // expand the clique
+                cliqueSoFar.set(invertedMap.get(neighbor));
+                searchClique(maxDepth, cliqueSoFar, depthSoFar, neighbor);
+                // back to the snapshot clique
+                cliqueSoFar.set(cliqueLength, cliqueSoFar.length(), false);
+            }
+        }
+
+        // update maximal clique info
+        updateMaximalClique(cliqueSoFar);
+    }
+
+    // update the maximal clique to a larger one if it exists
+    private void updateMaximalClique(BitSet cliqueSoFar) {
+        int cliqueSize = cliqueSoFar.cardinality();
+        if (cliqueSize > largestCliqueSizeSoFar) {
+            currentMaximalCliques.clear();
+            currentMaximalCliques.add((BitSet) cliqueSoFar.clone());
+            largestCliqueSizeSoFar = cliqueSize;
+        } else if (cliqueSize == largestCliqueSizeSoFar) {
+            currentMaximalCliques.add((BitSet) cliqueSoFar.clone());
+        } else {
+            return;
+        }
+    }
+
+    //should we test the vertex newVertex?
+    private boolean isTested(VLongWritable newVertex, BitSet cliqueSoFar) {
+        int index = invertedMap.get(newVertex);
+        int largestSetIndex = cliqueSoFar.length() - 1;
+        if (index > largestSetIndex) {
+            // we only return cliques with vertexes in the ascending order
+            // hence, the new vertex must be larger than the largesetSetIndex in the clique
+            return false;
+        } else {
+            // otherwise, we think the vertex is "tested"
+            return true;
+        }
+    }
+
+    // will adding the newVertex yield a bigger clique?
+    private boolean isClique(VLongWritable newVertex, BitSet cliqueSoFar) {
+        AdjacencyListWritable adj = map.get(newVertex);
+        // check whether each existing vertex is in the neighbor set of newVertex
+        for (int i = 0; i < cliqueSoFar.length();) {
+            i = cliqueSoFar.nextSetBit(i);
+            VLongWritable v = vertexList.get(i);
+            if (!adj.isNeighbor(v)) {
+                return false;
+            }
+            i++;
+        }
+        return true;
+    }
+
+    @Override
+    public void compute(Iterator<AdjacencyListWritable> msgIterator) {
+        if (getSuperstep() == 1) {
+            sortEdges();
+            sendMsg(getEdges());
+        } else if (getSuperstep() == 2) {
+            updateCurrentMaximalCliques(msgIterator);
+        } else {
+            voteToHalt();
+        }
+    }
+
+    private void sendMsg(List<Edge<VLongWritable, NullWritable>> edges) {
+        for (int i = 0; i < edges.size(); i++) {
+            if (edges.get(i).getDestVertexId().get() < getVertexId().get()) {
+                // only add emit for the vertexes whose id is smaller than adjListLong[0] 
+                // to avoid the duplicate removal step,
+                // because all the resulting cliques will have vertexes in the ascending order.
+                getVertexValue().reset();
+                AdjacencyListWritable msg = new AdjacencyListWritable();
+                msg.setSource(getVertexId());
+                for (int j = i + 1; j < edges.size(); j++) {
+                    msg.addNeighbor(edges.get(j).getDestVertexId());
+                }
+                sendMsg(edges.get(i).getDestVertexId(), msg);
+            }
+        }
+    }
+
+    /**
+     * Maximal Clique VertexWriter
+     */
+    public static class MaximalCliqueVertexWriter extends
+            TextVertexWriter<VLongWritable, CliquesWritable, NullWritable> {
+        public MaximalCliqueVertexWriter(RecordWriter<Text, Text> lineRecordWriter) {
+            super(lineRecordWriter);
+        }
+
+        @Override
+        public void writeVertex(Vertex<VLongWritable, CliquesWritable, NullWritable, ?> vertex) throws IOException,
+                InterruptedException {
+            getRecordWriter().write(new Text(vertex.getVertexId().toString()),
+                    new Text(vertex.getVertexValue().toString()));
+        }
+    }
+
+    /**
+     * output format for maximal clique
+     */
+    public static class MaximalCliqueVertexOutputFormat extends
+            TextVertexOutputFormat<VLongWritable, CliquesWritable, NullWritable> {
+
+        @Override
+        public VertexWriter<VLongWritable, CliquesWritable, NullWritable> createVertexWriter(TaskAttemptContext context)
+                throws IOException, InterruptedException {
+            RecordWriter<Text, Text> recordWriter = textOutputFormat.getRecordWriter(context);
+            return new MaximalCliqueVertexWriter(recordWriter);
+        }
+
+    }
+}
diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/TextMaximalCliqueInputFormat.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/TextMaximalCliqueInputFormat.java
new file mode 100644
index 0000000..ec7b32c
--- /dev/null
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/TextMaximalCliqueInputFormat.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2009-2010 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.uci.ics.pregelix.example.maximalclique;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.NullWritable;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.mapreduce.InputSplit;
+import org.apache.hadoop.mapreduce.RecordReader;
+import org.apache.hadoop.mapreduce.TaskAttemptContext;
+
+import edu.uci.ics.pregelix.api.graph.Vertex;
+import edu.uci.ics.pregelix.api.io.VertexReader;
+import edu.uci.ics.pregelix.api.io.text.TextVertexInputFormat;
+import edu.uci.ics.pregelix.api.io.text.TextVertexInputFormat.TextVertexReader;
+import edu.uci.ics.pregelix.api.util.BspUtils;
+import edu.uci.ics.pregelix.example.io.VLongWritable;
+
+public class TextMaximalCliqueInputFormat extends
+        TextVertexInputFormat<VLongWritable, CliquesWritable, NullWritable, AdjacencyListWritable> {
+
+    @Override
+    public VertexReader<VLongWritable, CliquesWritable, NullWritable, AdjacencyListWritable> createVertexReader(
+            InputSplit split, TaskAttemptContext context) throws IOException {
+        return new TextMaximalCliqueGraphReader(textInputFormat.createRecordReader(split, context));
+    }
+}
+
+@SuppressWarnings("rawtypes")
+class TextMaximalCliqueGraphReader extends
+        TextVertexReader<VLongWritable, CliquesWritable, NullWritable, AdjacencyListWritable> {
+
+    private final static String separator = " ";
+    private Vertex vertex;
+    private VLongWritable vertexId = new VLongWritable();
+    private List<VLongWritable> pool = new ArrayList<VLongWritable>();
+    private int used = 0;
+
+    public TextMaximalCliqueGraphReader(RecordReader<LongWritable, Text> lineRecordReader) {
+        super(lineRecordReader);
+    }
+
+    @Override
+    public boolean nextVertex() throws IOException, InterruptedException {
+        return getRecordReader().nextKeyValue();
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public Vertex<VLongWritable, CliquesWritable, NullWritable, AdjacencyListWritable> getCurrentVertex()
+            throws IOException, InterruptedException {
+        used = 0;
+        if (vertex == null)
+            vertex = (Vertex) BspUtils.createVertex(getContext().getConfiguration());
+        vertex.getMsgList().clear();
+        vertex.getEdges().clear();
+
+        vertex.reset();
+        Text line = getRecordReader().getCurrentValue();
+        String[] fields = line.toString().split(separator);
+
+        if (fields.length > 0) {
+            /**
+             * set the src vertex id
+             */
+            long src = Long.parseLong(fields[0]);
+            vertexId.set(src);
+            vertex.setVertexId(vertexId);
+            long dest = -1L;
+
+            /**
+             * set up edges
+             */
+            for (int i = 1; i < fields.length; i++) {
+                dest = Long.parseLong(fields[i]);
+                VLongWritable destId = allocate();
+                destId.set(dest);
+                vertex.addEdge(destId, null);
+            }
+        }
+        return vertex;
+    }
+
+    private VLongWritable allocate() {
+        if (used >= pool.size()) {
+            VLongWritable value = new VLongWritable();
+            pool.add(value);
+            used++;
+            return value;
+        } else {
+            VLongWritable value = pool.get(used);
+            used++;
+            return value;
+        }
+    }
+}