diff --git a/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetricsUnitTest.java b/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetricsUnitTest.java
index 6ece527ce..9031ea7f1 100755
--- a/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetricsUnitTest.java
+++ b/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetricsUnitTest.java
@@ -135,7 +135,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertEquals(eval.getGenotype("test1_sample2").getType().ordinal(), 2);
         Assert.assertEquals(truth.getGenotype("test1_sample2").getType().ordinal(),1);
@@ -185,7 +185,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertEquals(eval.getGenotype("test1_sample2").getType().ordinal(), 2);
         Assert.assertEquals(truth.getGenotype("test1_sample2").getType().ordinal(),2);
@@ -205,7 +205,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         codec = new VCFCodec();
         evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertEquals(eval.getGenotype("test1_sample2").getType().ordinal(), 2);
         Assert.assertEquals(truth.getGenotype("test1_sample2").getType().ordinal(),2);
@@ -260,7 +260,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertEquals(metrics.getGenotypeConcordance("test1_sample1").getnMismatchingAlt(),1);
         Assert.assertEquals(metrics.getGenotypeConcordance("test1_sample2").getTable()[2][1],0);
@@ -313,7 +313,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertEquals(metrics.getGenotypeConcordance("test1_sample2").getnMismatchingAlt(),0);
         Assert.assertEquals(metrics.getGenotypeConcordance("test1_sample2").getTable()[2][1],0);
@@ -362,7 +362,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         metrics.update(eval,truth);
         Assert.assertTrue(eval.getGenotype("test1_sample2").getType().equals(GenotypeType.UNAVAILABLE));
         Assert.assertEquals(metrics.getGenotypeConcordance("test1_sample2").getnMismatchingAlt(),0);
@@ -516,7 +516,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_2_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_2_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
 
         for ( Pair<VariantContext,VariantContext> contextPair : data ) {
             VariantContext eval = contextPair.getFirst();
@@ -550,7 +550,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_1_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
         int[][] table = metrics.getOverallGenotypeConcordance().getTable();
         // set up the table
         table[0] = new int[] {30, 12, 7, 5, 6, 0};
@@ -585,8 +585,8 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_3_HEADER_1))));
         VCFHeader disjointCompHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_3_HEADER_2))));
         VCFHeader overlapCompHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_3_HEADER_3))));
-        ConcordanceMetrics disjointMetrics = new ConcordanceMetrics(evalHeader,disjointCompHeader,false);
-        ConcordanceMetrics overlapMetrics = new ConcordanceMetrics(evalHeader,overlapCompHeader,false);
+        ConcordanceMetrics disjointMetrics = new ConcordanceMetrics(evalHeader,disjointCompHeader,null);
+        ConcordanceMetrics overlapMetrics = new ConcordanceMetrics(evalHeader,overlapCompHeader,null);
 
         // test what happens if you put in disjoint sets and start making requests
         Assert.assertEquals(0,disjointMetrics.getPerSampleGenotypeConcordance().size());
@@ -716,7 +716,7 @@ public class ConcordanceMetricsUnitTest extends BaseTest {
         VCFCodec codec = new VCFCodec();
         VCFHeader evalHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_2_HEADER))));
         VCFHeader compHeader = (VCFHeader)codec.readActualHeader(codec.makeSourceFromStream(new PositionalBufferedStream(new StringBufferInputStream(TEST_2_HEADER))));
-        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,false);
+        ConcordanceMetrics metrics = new ConcordanceMetrics(evalHeader,compHeader,null);
 
         List<Pair<VariantContext,VariantContext>> data = getData7();
 
diff --git a/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordanceIntegrationTest.java b/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordanceIntegrationTest.java
index 830b9169d..0348657c9 100755
--- a/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordanceIntegrationTest.java
+++ b/protected/gatk-protected/src/test/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordanceIntegrationTest.java
@@ -60,11 +60,11 @@ public class GenotypeConcordanceIntegrationTest extends WalkerTest {
     }
 
     @Test
-    public void testIndelConcordance() {
+    public void testIndelConcordanceWithSiteOutput() {
         WalkerTestSpec spec = new WalkerTestSpec(
-                baseTestString("NA12878.Jan2013.haplotypeCaller.subset.indels.vcf", "NA12878.Jan2013.bestPractices.subset.indels.vcf"),
-                0,
-                Arrays.asList("e4368146ffed2c6abf8265f5fbc5875d")
+                baseTestString("NA12878.Jan2013.haplotypeCaller.subset.indels.vcf", "NA12878.Jan2013.bestPractices.subset.indels.vcf") + " -sites %s",
+                2,
+                Arrays.asList("e4368146ffed2c6abf8265f5fbc5875d","1f441f00dd4243982502722c981a1e51")
         );
 
         executeTest("test indel concordance", spec);
diff --git a/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetrics.java b/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetrics.java
index 395e24604..c5cf997c2 100755
--- a/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetrics.java
+++ b/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/ConcordanceMetrics.java
@@ -32,6 +32,7 @@ import org.broadinstitute.sting.utils.variant.GATKVariantContextUtils;
 import org.broadinstitute.variant.variantcontext.*;
 import org.broadinstitute.variant.vcf.VCFHeader;
 
+import java.io.PrintStream;
 import java.util.*;
 
 /**
@@ -39,12 +40,12 @@ import java.util.*;
  * */
 public class ConcordanceMetrics {
 
-    private Map<String,GenotypeConcordanceTable> perSampleGenotypeConcordance;
-    private GenotypeConcordanceTable overallGenotypeConcordance;
-    private SiteConcordanceTable overallSiteConcordance;
-    private boolean printInterestingSites;
+    final private Map<String,GenotypeConcordanceTable> perSampleGenotypeConcordance;
+    final private GenotypeConcordanceTable overallGenotypeConcordance;
+    final private SiteConcordanceTable overallSiteConcordance;
+    final PrintStream sitesFile;
 
-    public ConcordanceMetrics(VCFHeader evaluate, VCFHeader truth, boolean printSitesEnabled) {
+    public ConcordanceMetrics(VCFHeader evaluate, VCFHeader truth, PrintStream inputSitesFile) {
         HashSet<String> overlappingSamples = new HashSet<String>(evaluate.getGenotypeSamples());
         overlappingSamples.retainAll(truth.getGenotypeSamples());
         perSampleGenotypeConcordance = new HashMap<String, GenotypeConcordanceTable>(overlappingSamples.size());
@@ -53,7 +54,12 @@ public class ConcordanceMetrics {
         }
         overallGenotypeConcordance = new GenotypeConcordanceTable();
         overallSiteConcordance = new SiteConcordanceTable();
-        printInterestingSites = printSitesEnabled;
+        sitesFile = inputSitesFile;
+        if (sitesFile != null) printSitesFileHeader();
+    }
+
+    private void printSitesFileHeader() {
+        sitesFile.println("Locus\tSample\tTruth Genotype\tEval Genotype");
     }
 
     public GenotypeConcordanceTable getOverallGenotypeConcordance() {
@@ -134,11 +140,8 @@ public class ConcordanceMetrics {
             }
             perSampleGenotypeConcordance.get(sample).update(evalGenotype,truthGenotype,alleleTruth,truthRef);
             doPrint = overallGenotypeConcordance.update(evalGenotype,truthGenotype,alleleTruth,truthRef);
-            if(printInterestingSites && doPrint)
-                System.out.println(eval.getChr() + ":" + eval.getStart() + "\t truth is:" + truthGenotype.getType() + "\t eval is:" + evalGenotype.getType());
-
-                //Below is code to print out mismatched alternate alleles
-                //System.out.println(eval.getChr() + ":" + eval.getStart() + "\t truth is:" + truthGenotype.getAlleles() + "\t eval is:" + evalGenotype.getAlleles());
+            if(sitesFile != null && doPrint)
+                sitesFile.println(eval.getChr() + ":" + eval.getStart() + "\t" + sample + "\t" + truthGenotype.getType() + "\t" + evalGenotype.getType());
         }
     }
 
diff --git a/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordance.java b/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordance.java
index 1bef3134a..0cfef0b65 100755
--- a/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordance.java
+++ b/public/gatk-framework/src/main/java/org/broadinstitute/sting/gatk/walkers/variantutils/GenotypeConcordance.java
@@ -246,13 +246,12 @@ public class GenotypeConcordance extends RodWalker<List<Pair<VariantContext,Vari
 
     /**
      * Print sites where genotypes are mismatched between callsets along with annotations giving the genotype of each callset
-     * Outputs directly to System.out.  Super classy.
+     * to the given filename
      *
-     * NOTE: doesn't currently differentiate between samples, so there may be repeats
      */
-    @Hidden
-    @Argument(shortName="sites", fullName = "printInterestingSites", required=false)
-    protected boolean printSites = false;
+
+    @Argument(shortName = "sites",required = false,fullName = "printInterestingSites", doc="File to output the discordant sites and genotypes.")
+    private PrintStream sitesFile = null;
 
     @Output
     PrintStream out;
@@ -285,7 +284,7 @@ public class GenotypeConcordance extends RodWalker<List<Pair<VariantContext,Vari
         evalSamples = evalHeader.getGenotypeSamples();
         VCFHeader compHeader = headerMap.get(compBinding.getName());
         compSamples = compHeader.getGenotypeSamples();
-        return new ConcordanceMetrics(evalHeader,compHeader, printSites);
+        return new ConcordanceMetrics(evalHeader,compHeader, sitesFile);
     }