diff --git a/gtsam/inference/BayesTree-inl.h b/gtsam/inference/BayesTree-inl.h
index 411f0bba7..5d2a64627 100644
--- a/gtsam/inference/BayesTree-inl.h
+++ b/gtsam/inference/BayesTree-inl.h
@@ -58,17 +58,17 @@ namespace gtsam {
 
 	/* ************************************************************************* */
 	template<class CONDITIONAL, class CLIQUE>
-	void BayesTree<CONDITIONAL,CLIQUE>::saveGraph(const std::string &s) const {
+	void BayesTree<CONDITIONAL,CLIQUE>::saveGraph(const std::string &s, const IndexFormatter& indexFormatter) const {
 		if (!root_.get()) throw std::invalid_argument("the root of Bayes tree has not been initialized!");
 		std::ofstream of(s.c_str());
 		of<< "digraph G{\n";
-		saveGraph(of, root_);
+		saveGraph(of, root_, indexFormatter);
 		of<<"}";
 		of.close();
 	}
 
 	template<class CONDITIONAL, class CLIQUE>
-	void BayesTree<CONDITIONAL,CLIQUE>::saveGraph(std::ostream &s, sharedClique clique, int parentnum) const {
+	void BayesTree<CONDITIONAL,CLIQUE>::saveGraph(std::ostream &s, sharedClique clique, const IndexFormatter& indexFormatter, int parentnum) const {
 		static int num = 0;
 		bool first = true;
 		std::stringstream out;
@@ -78,7 +78,7 @@ namespace gtsam {
 
 		BOOST_FOREACH(Index index, clique->conditional_->frontals()) {
 			if(!first) parent += ","; first = false;
-			parent +=  (boost::format("%1%")%index).str();;
+			parent += indexFormatter(index);
 		}
 
 		if( clique != root_){
@@ -89,7 +89,7 @@ namespace gtsam {
 		first = true;
 		BOOST_FOREACH(Index sep, clique->conditional_->parents()) {
 			if(!first) parent += ","; first = false;
-			parent += (boost::format("%1%")%sep).str();
+			parent += indexFormatter(sep);
 		}
 		parent += "\"];\n";
 		s << parent;
@@ -97,7 +97,7 @@ namespace gtsam {
 
 		BOOST_FOREACH(sharedClique c, clique->children_) {
 			num++;
-			saveGraph(s, c, parentnum);
+			saveGraph(s, c, indexFormatter, parentnum);
 		}
 	}
 
diff --git a/gtsam/inference/BayesTree.h b/gtsam/inference/BayesTree.h
index 8c7ba1a39..c62af258a 100644
--- a/gtsam/inference/BayesTree.h
+++ b/gtsam/inference/BayesTree.h
@@ -25,6 +25,7 @@
 #include <boost/function.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/make_shared.hpp>
+#include <boost/lexical_cast.hpp>
 
 #include <gtsam/base/types.h>
 #include <gtsam/base/FastVector.h>
@@ -33,6 +34,7 @@
 #include <gtsam/inference/BayesTreeCliqueBase.h>
 #include <gtsam/inference/IndexConditional.h>
 #include <gtsam/linear/VectorValues.h>
+#include <gtsam/nonlinear/Key.h>
 
 namespace gtsam {
 
@@ -97,7 +99,7 @@ namespace gtsam {
 		Nodes nodes_;
 
 		/** private helper method for saving the Tree to a text file in GraphViz format */
-		void saveGraph(std::ostream &s, sharedClique clique,
+		void saveGraph(std::ostream &s, sharedClique clique, const IndexFormatter& indexFormatter,
 				int parentnum = 0) const;
 
 		/** Gather data on a single clique */
@@ -232,7 +234,7 @@ namespace gtsam {
 		 */
 
 		/** saves the Tree to a text file in GraphViz format */
-		void saveGraph(const std::string& s) const;
+		void saveGraph(const std::string& s, const IndexFormatter& indexFormatter = &boost::lexical_cast<std::string, Index>) const;
 
 		/// @}
 		/// @name Advanced Interface
diff --git a/gtsam/nonlinear/NonlinearISAM.cpp b/gtsam/nonlinear/NonlinearISAM.cpp
index 17fba2432..3bddbb635 100644
--- a/gtsam/nonlinear/NonlinearISAM.cpp
+++ b/gtsam/nonlinear/NonlinearISAM.cpp
@@ -30,8 +30,21 @@ using namespace std;
 namespace gtsam {
 
 /* ************************************************************************* */
-void NonlinearISAM::saveGraph(const string& s) const {
-  isam_.saveGraph(s);
+void NonlinearISAM::saveGraph(const string& s, const KeyFormatter& keyFormatter) const {
+
+  // Create an index formatter that looks up the Key in an inverse ordering, then
+  // formats the key using the provided key formatter.
+  struct OrderingIndexFormatter {
+    Ordering::InvertedMap inverseOrdering;
+    const KeyFormatter& keyFormatter;
+    OrderingIndexFormatter(const Ordering& ordering, const KeyFormatter& keyFormatter) :
+        inverseOrdering(ordering.invert()), keyFormatter(keyFormatter) {}
+    string operator()(Index index) {
+      return keyFormatter(inverseOrdering.at(index));
+    }
+  };
+
+  isam_.saveGraph(s, OrderingIndexFormatter(ordering_, keyFormatter));
 }
 
 /* ************************************************************************* */
diff --git a/gtsam/nonlinear/NonlinearISAM.h b/gtsam/nonlinear/NonlinearISAM.h
index 7a7b9cd2c..fc2f69f55 100644
--- a/gtsam/nonlinear/NonlinearISAM.h
+++ b/gtsam/nonlinear/NonlinearISAM.h
@@ -92,7 +92,7 @@ public:
 	void printStats() const;
 
   /** saves the Tree to a text file in GraphViz format */
-  void saveGraph(const std::string& s) const;
+  void saveGraph(const std::string& s, const KeyFormatter& keyFormatter = DefaultKeyFormatter) const;
 
 	/// @}
 	/// @name Advanced Interface