diff --git a/org.intrace/build.xml b/org.intrace/build.xml
index a7b351b..53698e6 100644
--- a/org.intrace/build.xml
+++ b/org.intrace/build.xml
@@ -423,6 +423,14 @@
       <jvmarg value="-javaagent:build/jars/intrace-agent.jar=[instru-true" />
     </java>
   </target>
+  <target name="example3" depends="jar,example_build">
+    <java classname="example.InstrumentMeLaunch" fork="true">
+      <classpath>
+        <pathelement path="./build/test" />
+      </classpath>
+      <jvmarg value="-javaagent:build/jars/intrace-agent.jar=[instru-true" />
+    </java>
+  </target>
 
 
   <target name="waitexample" depends="jar,example_build">
diff --git a/org.intrace/src/org/intrace/agent/AgentSettings.java b/org.intrace/src/org/intrace/agent/AgentSettings.java
index 645983b..1b57059 100644
--- a/org.intrace/src/org/intrace/agent/AgentSettings.java
+++ b/org.intrace/src/org/intrace/agent/AgentSettings.java
@@ -40,6 +40,7 @@ private InstrCriteria classesToExclude = null;
   private boolean instruEnabled = true;
   private boolean saveTracedClassfiles = false;
   private boolean verboseMode = false;  
+  private boolean _instrumentImplementors = false;
 
   
 
@@ -54,6 +55,7 @@ private InstrCriteria classesToExclude = null;
     instruEnabled = oldInstance.isInstrumentationEnabled();
     saveTracedClassfiles = oldInstance.saveTracedClassfiles();
     verboseMode = oldInstance.isVerboseMode();
+    _instrumentImplementors = oldInstance.instrumentImplementors();
   }
   public AgentSettings(String args)
   {
@@ -138,8 +140,17 @@ public void parseArgs(String args)
       this.classesToExclude = new InstrCriteria(classExcludeRegexStr);
       this.classesToExclude.verboseLogger = this;
     }
+    else if (arg.toLowerCase(Locale.ROOT).equals(
+                                      AgentConfigConstants.INSTRUMENT_IMPLEMENTORS
+                                          + "true"))
+    {
+        this._instrumentImplementors = true;
+    }
   }
 
+  public boolean instrumentImplementors() {
+    return _instrumentImplementors;
+  }
   public boolean isWaitStart()
   {
     return waitStart;
diff --git a/org.intrace/src/org/intrace/agent/ClassTransformer.java b/org.intrace/src/org/intrace/agent/ClassTransformer.java
index 98eb80d..5882249 100644
--- a/org.intrace/src/org/intrace/agent/ClassTransformer.java
+++ b/org.intrace/src/org/intrace/agent/ClassTransformer.java
@@ -21,6 +21,7 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentSkipListSet;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.intrace.agent.server.AgentClientConnection;
 import org.intrace.agent.server.AgentServer;
@@ -51,11 +52,21 @@ public class ClassTransformer implements ClassFileTransformer
    * Set of modified class names
    */
   private final Set<ComparableClassName> modifiedClasses = new ConcurrentSkipListSet<ComparableClassName>();
+  /**
+   * Javadoc and stacktraces show that ConcurrentSkipListSet.size() takes up large amount of time.
+   * This variable will be used to store count.
+   */
+  private final AtomicInteger modifiedClassesCount = new AtomicInteger(); 
 
   /**
    * Map of all seen class names
    */
   private final Set<ComparableClassName> allClasses = new ConcurrentSkipListSet<ComparableClassName>();
+  /**
+   * Javadoc and stacktraces show that ConcurrentSkipListSet.size() takes up large amount of time.
+   * This variable will be used to store count.
+   */
+  private final AtomicInteger allClassesCount = new AtomicInteger();
 
   /**
    * Instrumentation interface.
@@ -90,6 +101,8 @@ public class ClassTransformer implements ClassFileTransformer
     {
       TraceHandler.INSTANCE.writeTraceOutput("DEBUG: " + settings.toString());
     }
+    this.allClassesCount.set(0);
+    this.modifiedClassesCount.set(0);
   }
 
   /**
@@ -110,6 +123,7 @@ public class ClassTransformer implements ClassFileTransformer
       ClassAnalysis analysis = new ClassAnalysis();
       cr.accept(analysis, 0);
 
+	//System.out.println("getInstrumentedClassBytes [" + xiClassName + "]");
       InstrumentedClassWriter writer = new InstrumentedClassWriter(xiClassName,
                                                                    cr, analysis,
                                                                    shouldInstrument,
@@ -152,11 +166,13 @@ public class ClassTransformer implements ClassFileTransformer
                                                      ProtectionDomain protectionDomain,
                                                      byte[] originalClassfile)
   {
+//	System.out.println("itbcfi [" + className + "] klass [" + klass.getName() + "] protectionDomain [" + protectionDomain + "]");
     ComparableClassName compklass = new ComparableClassName(className,
                                                             klassloader);
 
     // Record all class names which get this far
     allClasses.add(compklass);
+    allClassesCount.incrementAndGet();
 
     // Don't modify anything if tracing is disabled
     if (!settings.isInstrumentationEnabled())
@@ -201,13 +217,15 @@ public class ClassTransformer implements ClassFileTransformer
     {
       // Actually we should modify if any of the interfaces match the regex
       boolean matchedInterface = false;
-      for(String klassInterface : getInterfaces(className, originalClassfile))
-      {
-        if ((settings.getClassRegex() != null)
-            && matches(settings.getClassRegex(), klassInterface))
-        {
-          matchedInterface |= true;
-        }
+      if (originalClassfile !=null && settings.instrumentImplementors() ) {
+          for(String klassInterface : getInterfaces(className, originalClassfile))
+          {
+            if ((settings.getClassRegex() != null)
+                && matches(settings.getClassRegex(), klassInterface))
+            {
+              matchedInterface |= true;
+           }
+          }
       }
 
       if(!matchedInterface)
@@ -300,8 +318,8 @@ public class ClassTransformer implements ClassFileTransformer
     {
       String className = internalClassName.replace('/', '.');
       ComparableClassName compclass = new ComparableClassName(className, loader);
-      int modifiedSize = modifiedClasses.size();
-      int allClassesSize = allClasses.size();
+      int modifiedSize = modifiedClassesCount.get();
+      int allClassesSize = allClassesCount.get();
 
       boolean shouldInstrument = isToBeConsideredForInstrumentation(classBeingRedefined, loader,
                                                                     className, protectionDomain,
@@ -342,6 +360,7 @@ public class ClassTransformer implements ClassFileTransformer
         }
 
         modifiedClasses.add(compclass);
+        modifiedClassesCount.getAndIncrement();
 
         sendStatusUpdate(modifiedSize, allClassesSize);
 
@@ -350,6 +369,7 @@ public class ClassTransformer implements ClassFileTransformer
       else
       {
         modifiedClasses.remove(compclass);
+        modifiedClassesCount.decrementAndGet();
 
         sendStatusUpdate(modifiedSize, allClassesSize);
         return null;
@@ -409,13 +429,13 @@ public class ClassTransformer implements ClassFileTransformer
         try
         {
           StatusUpdate update = statusHolder.getStatus();
-          int newModifiedSize = modifiedClasses.size();
-          int newAllClassesSize = allClasses.size();
+          int newModifiedSize = modifiedClassesCount.get();
+          int newAllClassesSize = allClassesCount.get();
           if (!bulkUpdateActive.get() &&
               ((newModifiedSize != update.modifiedSize) ||
                (newAllClassesSize != update.allClassesSize)))
           {
-            broadcastStatus(modifiedClasses.size(), allClasses.size());
+            broadcastStatus(modifiedClassesCount.get(), allClassesCount.get());
           }
         }
         catch (InterruptedException e)
@@ -524,9 +544,9 @@ public class ClassTransformer implements ClassFileTransformer
   {
     Map<String, String> settingsMap = settings.getSettingsMap();
     settingsMap.put(AgentConfigConstants.STCLS,
-                    Integer.toString(allClasses.size()));
+                    Integer.toString(allClassesCount.get()));
     settingsMap.put(AgentConfigConstants.STINST,
-                    Integer.toString(modifiedClasses.size()));
+                    Integer.toString(modifiedClassesCount.get()));
     return settingsMap;
   }
 
@@ -551,12 +571,12 @@ public class ClassTransformer implements ClassFileTransformer
     else if (oldSettings.isInstrumentationEnabled() != settings
                                                                .isInstrumentationEnabled())
     {
-//      System.out.println("## Settings Changed");
+      //System.out.println("## Settings Changed");
       setInstrumentationEnabled(settings.isInstrumentationEnabled());
     }
     else if (!Arrays.equals(oldSettings.getClassRegex(), settings.getClassRegex()))
     {
-//      System.out.println("## Settings Changed");
+      //System.out.println("## Settings Changed");
       Set<ComparableClass> klasses = new HashSet<ComparableClass>(getModifiedClasses());
       modifiedClasses.clear();
       klasses.addAll(getLoadedClassesForModification());
@@ -564,7 +584,7 @@ public class ClassTransformer implements ClassFileTransformer
     }
     else if (!Arrays.equals(oldSettings.getExcludeClassRegex(), settings.getExcludeClassRegex()))
     {
-//      System.out.println("## Settings Changed");
+      //System.out.println("## Settings Changed");
       Set<ComparableClass> klasses = new HashSet<ComparableClass>(getModifiedClasses());
       modifiedClasses.clear();
       klasses.addAll(getLoadedClassesForModification());
@@ -573,7 +593,7 @@ public class ClassTransformer implements ClassFileTransformer
     else if (oldSettings.saveTracedClassfiles() != settings
                                                            .saveTracedClassfiles())
     {
-//      System.out.println("## Settings Changed");
+      //System.out.println("## Settings Changed");
       Set<ComparableClass> klasses = getModifiedClasses();
       modifiedClasses.clear();
       klasses.addAll(getLoadedClassesForModification());
@@ -656,7 +676,12 @@ public class ClassTransformer implements ClassFileTransformer
                              + loadedClass.getCanonicalName());
         }
       }
-      else
+      else  if (settings.instrumentImplementors() || isToBeConsideredForInstrumentation(
+                                                  loadedClass,
+                                                  loadedClass.getClassLoader(),
+                                                  loadedClass.getName(),
+                                                  loadedClass.getProtectionDomain(),
+						  null ))
       {
         ComparableClass loadedKlass = new ComparableClass(loadedClass);
         unmodifiedKlasses.add(loadedKlass);
@@ -665,6 +690,18 @@ public class ClassTransformer implements ClassFileTransformer
     return unmodifiedKlasses;
   }
 
+/*
+The catch block in this method should have caught the following, but it did not.
+Need to figure out why.
+<pre>
+     [java] java.lang.VerifyError
+     [java]     at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
+     [java]     at sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:144)
+     [java]     at org.intrace.agent.ClassTransformer.instrumentKlasses(ClassTransformer.java:719)
+     [java]     at org.intrace.agent.ClassTransformer.getResponse(ClassTransformer.java:584)
+     [java]     at org.intrace.agent.server.AgentClientConnection.runMethod(AgentClientConnection.java:118)
+</pre>
+*/
   public void instrumentKlasses(Set<ComparableClass> klasses)
   {
     if (!inst.isRetransformClassesSupported())
@@ -692,10 +729,10 @@ public class ClassTransformer implements ClassFileTransformer
           inst.retransformClasses(klass.klass);
 
           countNumClasses++;
-          if ((countNumClasses % 100) == 0)
-          {
+//          if ((countNumClasses % 100) == 0)
+//          {
             broadcastProgress(countNumClasses, totalNumClasses);
-          }
+//          }
         }
         catch (Throwable e)
         {
@@ -711,7 +748,7 @@ public class ClassTransformer implements ClassFileTransformer
     finally
     {
       bulkUpdateActive.set(false);
-      broadcastStatus(modifiedClasses.size(), allClasses.size());
+      broadcastStatus(modifiedClasses.size(), allClassesCount.get());
     }
   }
 
diff --git a/org.intrace/src/org/intrace/agent/InstrumentedClassWriter.java b/org.intrace/src/org/intrace/agent/InstrumentedClassWriter.java
index c707020..e1cff72 100644
--- a/org.intrace/src/org/intrace/agent/InstrumentedClassWriter.java
+++ b/org.intrace/src/org/intrace/agent/InstrumentedClassWriter.java
@@ -79,6 +79,7 @@ public class InstrumentedClassWriter extends ClassWriter
 	  	  sb.append(InstrCriteria.CLASS_METHOD_DELIMITER);
 	  	  sb.append(name);
 	  	  sb.append(desc);
+		//System.out.println("@#%:" + sb.toString() );
 	      TraceHandler.INSTANCE.writeTraceOutput("DEBUG: method signature: " + sb.toString());
 	    }	  
     MethodVisitor mv = super.visitMethod(access, name, desc, signature,
diff --git a/org.intrace/src/org/intrace/output/trace/TraceHandler.java b/org.intrace/src/org/intrace/output/trace/TraceHandler.java
index d6f2393..88ed9ae 100644
--- a/org.intrace/src/org/intrace/output/trace/TraceHandler.java
+++ b/org.intrace/src/org/intrace/output/trace/TraceHandler.java
@@ -472,7 +472,7 @@ private static final Object STACK_ELE_DELIM = ",";
                          + "]:" + xiOutput;
 //    if (AgentHelper.getOutputSettings().isStdoutOutputEnabled())
 //    {
-////      System.out.println(traceString);
+//      System.out.println(traceString);
 //    }
 
     if (AgentHelper.getOutputSettings().isFileOutputEnabled())
diff --git a/org.intrace/src/org/intrace/shared/AgentConfigConstants.java b/org.intrace/src/org/intrace/shared/AgentConfigConstants.java
index d4826bc..a788176 100644
--- a/org.intrace/src/org/intrace/shared/AgentConfigConstants.java
+++ b/org.intrace/src/org/intrace/shared/AgentConfigConstants.java
@@ -24,6 +24,7 @@ public class AgentConfigConstants
   public static final String OPT_SERVER_PORT = "[serverport-";
   public static final String CALLBACK_PORT = "[callbackport-";
   public static final String EXIT_STACK_TRACE = "[exit-stack-trace-";
+  public static final String INSTRUMENT_IMPLEMENTORS = "[instrument-implementors";
   
   public static final String START_WAIT = "[startwait";
   public static final String START_ACTIVATE = "[startactivate";
@@ -39,5 +40,6 @@ public class AgentConfigConstants
     COMMANDS.add(OPT_SERVER_PORT + "<int>");
     COMMANDS.add(CALLBACK_PORT + "<int>");
     COMMANDS.add(EXIT_STACK_TRACE + "<true/false>");
+    COMMANDS.add(INSTRUMENT_IMPLEMENTORS + "<true/false>");
   }
 }
diff --git a/org.intrace/testsrc/example/InstrumentMe.java b/org.intrace/testsrc/example/InstrumentMe.java
new file mode 100644
index 0000000..3b33597
--- /dev/null
+++ b/org.intrace/testsrc/example/InstrumentMe.java
@@ -0,0 +1,20 @@
+package example;
+
+import java.util.Arrays;
+
+public class InstrumentMe implements Runnable
+{
+	private byte myField = 1;
+
+  @Override
+  public void run()
+  {
+      byteArg((byte) 0);
+  }
+
+  private void byteArg(byte arg)
+  {
+   this.myField = arg; 
+  }
+
+}
diff --git a/org.intrace/testsrc/example/InstrumentMeLaunch.java b/org.intrace/testsrc/example/InstrumentMeLaunch.java
new file mode 100644
index 0000000..a911c49
--- /dev/null
+++ b/org.intrace/testsrc/example/InstrumentMeLaunch.java
@@ -0,0 +1,27 @@
+package example;
+
+public class InstrumentMeLaunch 
+{
+	public static void main(String args[]) throws Exception {
+		System.out.println("Currently running sample code in background thread.");
+		System.out.println("Make sure this program has -javaagent:./path/to/intrace-agent.jar on its command line.");
+		System.out.println("Start InTrace GUI, download-able at https://mchr3k.github.io/org.intrace/");
+		System.out.println("'Connect' & then configure GUI to trace any of these patterns:\n\n");
+		System.out.println("example.InstrumentMe					-- to trace all methods in class example.InstrumentMe");
+		System.out.println("example.InstrumentMe					-- to trace all methods in class example.InstrumentMeLaunch");
+		System.out.println("example.InstrumentMe#<init>()V				-- to trace this single method.");
+		System.out.println("example.InstrumentMe#run()V					-- to trace this single method.");
+		System.out.println("example.InstrumentMe#byteArg(B)V				-- to trace this single method.");
+		System.out.println("example.InstrumentMeLaunch#<init>()V			-- to trace this single method.");
+		System.out.println("example.InstrumentMeLaunch#main([Ljava/lang/String;)V	-- to trace this single method.\n\n");
+     
+		System.out.println("Press Ctrl+C to quit this program.");
+		Runnable r = new InstrumentMe();
+		while(true) {
+			System.out.println("About to start thread.");
+			new Thread(r).start();
+			Thread.sleep(2000);
+			
+		}
+	}
+}
diff --git a/org.intrace/testsrc/org/intracetest/agent/AgentSettingsTest.java b/org.intrace/testsrc/org/intracetest/agent/AgentSettingsTest.java
index 420e77e..bc8e8aa 100644
--- a/org.intrace/testsrc/org/intracetest/agent/AgentSettingsTest.java
+++ b/org.intrace/testsrc/org/intracetest/agent/AgentSettingsTest.java
@@ -64,6 +64,25 @@ public class AgentSettingsTest extends TestCase
     assertEquals(settingsMap.get(AgentConfigConstants.VERBOSE_MODE), "true");
   }
 
+  public void testInstrumentImplementorsSetting() {
+    AgentSettings as1 = new AgentSettings(
+                                             AgentConfigConstants.INSTRUMENT_IMPLEMENTORS
+                                             + "true"
+                                             );
+    assertTrue( "unable to recognize parameter that instruments implementors of interfaces", as1.instrumentImplementors() );
+
+   AgentSettings as2 = new AgentSettings(
+                                             AgentConfigConstants.INSTRUMENT_IMPLEMENTORS
+                                             + "false"
+                                             );
+    assertFalse( "unable to recognize parameter that instruments implementors of interfaces",as2.instrumentImplementors() );
+
+  AgentSettings as3 = new AgentSettings("");
+    assertFalse( "unable to recognize parameter that instruments implementors of interfaces", as3.instrumentImplementors() );
+
+
+  }
+
   public void testInstrCriteria() {
 	InstrCriteria ic = new InstrCriteria("foo|bar");