Not 100% sure if subgraphs are to blame, but the traits of the attached graph include: 1. adjacency_iterator 2. in_edge_iterator 3. out_edge_iterator But fails to compile when I add a "inv_adjacency_iterator". Surely this iterator is basically the same as the in_edge_iterator, with a different return type? Gordon typedef boost::adjacency_list<boost::vecS, boost::listS, boost::bidirectionalS, GjsvizVertexProperty, GjsvizEdgeProperty, GjsvizGraphProperty > DigraphType; typedef DigraphType GraphType; typedef boost::graph_traits<GraphType> Traits; typedef Traits::adjacency_iterator adjacency_iterator; **** No Compile >>>>typedef Traits::inv_adjacency_iterator inv_adjacency_iterator; typedef Traits::in_edge_iterator in_edge_iterator; typedef Traits::out_edge_iterator out_edge_iterator;