diff --git a/protected/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngine.java b/protected/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngine.java
index 1d0c10795..4259dbdb6 100644
--- a/protected/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngine.java
+++ b/protected/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngine.java
@@ -385,11 +385,23 @@ public class UnifiedGenotyperEngine {
 
         boolean limitedContext = tracker == null || refContext == null || rawContext == null || stratifiedContexts == null;
 
+        // TODO TODO TODO TODO
+        // REFACTOR THIS FUNCTION, TOO UNWIELDY!!
+
         // initialize the data for this thread if that hasn't been done yet
         if ( afcm.get() == null ) {
             afcm.set(AFCalcFactory.createAFCalc(UAC, N, logger));
         }
 
+        // if input VC can't be genotyped, exit with either null VCC or, in case where we need to emit all sites, an empty call
+        if (!canVCbeGenotyped(vc))   {
+            if (UAC.OutputMode == OUTPUT_MODE.EMIT_ALL_SITES && !limitedContext)
+                return generateEmptyContext(tracker, refContext, stratifiedContexts, rawContext);
+            else
+                return null;
+
+        }
+
         // estimate our confidence in a reference call and return
         if ( vc.getNSamples() == 0 ) {
             if ( limitedContext )
@@ -544,6 +556,23 @@ public class UnifiedGenotyperEngine {
         return new VariantCallContext(vcCall, confidentlyCalled(phredScaledConfidence, PoFGT0));
     }
 
+    /**
+     * Determine whether input VC to calculateGenotypes() can be genotyped and AF can be computed.
+     * @param vc                                    Input VC
+     * @return                                      Status check
+     */
+    @Requires("vc != null")
+    protected boolean canVCbeGenotyped(final VariantContext vc) {
+        // protect against too many alternate alleles that we can't even run AF on:
+        if (vc.getNAlleles()> GenotypeLikelihoods.MAX_ALT_ALLELES_THAT_CAN_BE_GENOTYPED) {
+            logger.warn("Attempting to genotype more than "+GenotypeLikelihoods.MAX_ALT_ALLELES_THAT_CAN_BE_GENOTYPED +
+                    " alleles. Site will be skipped at location "+vc.getChr()+":"+vc.getStart());
+            return false;
+        }
+        else return true;
+
+    }
+
     private Map<String, AlignmentContext> getFilteredAndStratifiedContexts(UnifiedArgumentCollection UAC, ReferenceContext refContext, AlignmentContext rawContext, final GenotypeLikelihoodsCalculationModel.Model model) {
 
         if ( !BaseUtils.isRegularBase(refContext.getBase()) )
diff --git a/protected/java/test/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngineUnitTest.java b/protected/java/test/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngineUnitTest.java
index 23596db83..657cd9c0c 100644
--- a/protected/java/test/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngineUnitTest.java
+++ b/protected/java/test/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyperEngineUnitTest.java
@@ -50,10 +50,16 @@ package org.broadinstitute.sting.gatk.walkers.genotyper;
 // the imports for unit testing.
 
 
+import org.apache.commons.lang.ArrayUtils;
 import org.broadinstitute.sting.BaseTest;
 import org.broadinstitute.sting.gatk.GenomeAnalysisEngine;
 import org.broadinstitute.sting.gatk.arguments.GATKArgumentCollection;
 import org.broadinstitute.sting.utils.MathUtils;
+import org.broadinstitute.sting.utils.Utils;
+import org.broadinstitute.variant.variantcontext.Allele;
+import org.broadinstitute.variant.variantcontext.GenotypeLikelihoods;
+import org.broadinstitute.variant.variantcontext.VariantContext;
+import org.broadinstitute.variant.variantcontext.VariantContextBuilder;
 import org.testng.Assert;
 import org.testng.annotations.BeforeClass;
 import org.testng.annotations.BeforeMethod;
@@ -102,4 +108,23 @@ public class UnifiedGenotyperEngineUnitTest extends BaseTest {
         Assert.assertTrue(MathUtils.goodLog10Probability(ref), "Reference calculation wasn't a well formed log10 prob " + ref);
         Assert.assertEquals(ref, expected, TOLERANCE, "Failed reference confidence for single sample");
     }
+
+    @Test(enabled=true)
+    public void testTooManyAlleles() {
+
+        for ( Integer numAltAlleles = 0; numAltAlleles < 100; numAltAlleles++ )  {
+
+            Set<Allele> alleles = new HashSet<Allele>();
+            alleles.add(Allele.create("A", true));        // ref allele
+
+            for (int len = 1; len <=numAltAlleles; len++) {
+                // add alt allele of length len+1
+                alleles.add(Allele.create(Utils.dupString('A', len + 1), false));
+            }
+            final VariantContext vc = new VariantContextBuilder("test", "chr1", 1000, 1000, alleles).make();
+            final boolean result = ugEngine.canVCbeGenotyped(vc);
+            Assert.assertTrue(result == (vc.getNAlleles()<= GenotypeLikelihoods.MAX_ALT_ALLELES_THAT_CAN_BE_GENOTYPED));
+        }
+    }
+
 }
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