diff --git a/java/src/org/broadinstitute/sting/gatk/refdata/rodDbSNP.java b/java/src/org/broadinstitute/sting/gatk/refdata/rodDbSNP.java
index 6d145dbd8..3f87d596d 100644
--- a/java/src/org/broadinstitute/sting/gatk/refdata/rodDbSNP.java
+++ b/java/src/org/broadinstitute/sting/gatk/refdata/rodDbSNP.java
@@ -3,6 +3,7 @@ package org.broadinstitute.sting.gatk.refdata;
 import net.sf.samtools.util.SequenceUtil;
 import org.broadinstitute.sting.utils.*;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -94,9 +95,9 @@ public class rodDbSNP extends BasicReferenceOrderedDatum implements VariationRod
      * @return an alternate allele list
      */
     public List<String> getAlternateAlleleList() {
-        List<String> ret = getAlleleList();
-        for (String allele : ret)
-            if (allele.equals(getReference())) ret.remove(allele);
+        List<String> ret = new ArrayList<String>();
+        for (String allele : getAlleleList())
+            if (!allele.equals(getReference())) ret.add(allele);
         return ret;
     }
 
@@ -160,8 +161,8 @@ public class rodDbSNP extends BasicReferenceOrderedDatum implements VariationRod
     }
 
     /**
-     * gets the alternate base is the case of a SNP.  Throws an IllegalStateException in the case
-     * of
+     * gets the alternate base is the case of a SNP.  Throws a StingException when we can't parse out a
+     * single base to return, the site isn't a snp, or the site isn't biallelic
      *
      * @return a char, representing the alternate base
      */
@@ -175,7 +176,7 @@ public class rodDbSNP extends BasicReferenceOrderedDatum implements VariationRod
     }
 
     /**
-     * gets the reference base is the case of a SNP.  Throws an IllegalStateException if we're not a SNP
+     * gets the reference base is the case of a SNP.  Throws a StingException if we're not a SNP.
      *
      * @return a char, representing the alternate base
      */
@@ -276,7 +277,7 @@ public class rodDbSNP extends BasicReferenceOrderedDatum implements VariationRod
     }
 
     public boolean isBiallelic() {
-        return getAlleleList().size() == 2;
+        return getAlternateAlleleList().size() == 1;
     }
 
     public static rodDbSNP getFirstRealSNP(RODRecordList<ReferenceOrderedDatum> dbsnpList) {
diff --git a/java/src/org/broadinstitute/sting/oneoffprojects/walkers/ValidateDbSNPConversion.java b/java/src/org/broadinstitute/sting/oneoffprojects/walkers/ValidateDbSNPConversion.java
new file mode 100644
index 000000000..bb34119af
--- /dev/null
+++ b/java/src/org/broadinstitute/sting/oneoffprojects/walkers/ValidateDbSNPConversion.java
@@ -0,0 +1,117 @@
+package org.broadinstitute.sting.oneoffprojects.walkers;
+
+import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
+import org.broadinstitute.sting.gatk.contexts.ReferenceContext;
+import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
+import org.broadinstitute.sting.gatk.refdata.rodDbSNP;
+import org.broadinstitute.sting.gatk.walkers.RefWalker;
+import org.broadinstitute.sting.utils.Pair;
+
+import java.io.PrintStream;
+
+
+/**
+ * @author aaron
+ *
+ * Class ValidateDbSNPConversion
+ *
+ * a quick walker to validate the dbSNP conversion.
+ */
+public class ValidateDbSNPConversion extends RefWalker<Pair<Matrix.BASE, Matrix.BASE>, Matrix> {
+    @Override
+    public Pair<Matrix.BASE, Matrix.BASE> map(RefMetaDataTracker tracker, ReferenceContext ref, AlignmentContext context) {
+        if (!tracker.hasROD("dbsnp")) return null;
+        rodDbSNP rod = (rodDbSNP) tracker.lookup("dbSNP", null);
+        if (rod != null && rod.isSNP() && rod.isBiallelic()) {
+            return new Pair<Matrix.BASE, Matrix.BASE>(Matrix.BASE.toBase((byte) ref.getBase()), Matrix.BASE.toBase((byte) rod.getAlternativeBaseForSNP()));
+        }
+        return null;
+    }
+
+    /**
+     * Provide an initial value for reduce computations.
+     *
+     * @return Initial value of reduce.
+     */
+    @Override
+    public Matrix reduceInit() {
+        return new Matrix();
+    }
+
+    /**
+     * Reduces a single map with the accumulator provided as the ReduceType.
+     *
+     * @param value result of the map.
+     * @param sum   accumulator for the reduce.
+     *
+     * @return accumulator with result of the map taken into account.
+     */
+    @Override
+    public Matrix reduce(Pair<Matrix.BASE, Matrix.BASE> value, Matrix sum) {
+        if (value != null) sum.addValue(value.first,value.second);
+        return sum;
+    }
+
+    public void onTraversalDone(Matrix result) {
+        result.printStats(out);
+    }
+
+}
+
+
+class Matrix {
+    public enum BASE {
+        A((byte) 65), C((byte) 67), G((byte) 71), T((byte) 84), N((byte)78);
+        private byte val = 65;
+
+        BASE(byte val) {
+            this.val = val;
+        }
+
+        byte getVal() {
+            return val;
+        }
+
+        static BASE toBase(byte b) {
+            if (b > 96) b =- 32;
+            if (b == A.val) return A;
+            if (b == C.val) return C;
+            if (b == G.val) return G;
+            if (b == T.val) return T;
+            // we don't really care, let return N instead of: throw new UnsupportedOperationException("Unknown base " + b);
+            return N;
+        }
+    }
+
+    private int[][] mat = new int[BASE.values().length][BASE.values().length];
+
+    public void addValue(BASE ref, BASE alt) {
+        mat[ref.ordinal()][alt.ordinal()] += 1;
+    }
+
+    public void printStats(PrintStream stream) {
+        for (BASE a : BASE.values()) {
+            stream.print("ref " + a.toString() + ":");
+            for (BASE b : BASE.values()) {
+                stream.print(" " + mat[a.ordinal()][b.ordinal()]);
+            }
+            stream.println();
+        }
+    }
+
+    public void addMatrix(Matrix mt) {
+        for (BASE a : BASE.values()) {
+            for (BASE b : BASE.values()) {
+                mat[a.ordinal()][b.ordinal()] += mt.mat[a.ordinal()][b.ordinal()];
+            }
+        }
+    }
+
+    public Matrix() {
+        for (int x = 0; x < BASE.values().length; x++) {
+            for (int y = 0; y < BASE.values().length; y++) {
+                mat[x][y] = 0;
+            }
+        }
+    }
+}
\ No newline at end of file