I try to use the adjacency list from boost. I can fill the list with vertices and edges, but somehow I cannot access a specific vertex or edge. For example this is not working (see test.cpp): ** struct EdgeProperties { bool bConnectedBond; EdgeProperties(){bConnectedBond=false;} }; struct VertexProperties{ int index; int spin; bool bOnCluster; VertexProperties(): spin(){ bOnCluster = false;} ~VertexProperties(){ } }; typedef adjacency_list< vecS, vecS, bidirectionalS, VertexProperties, EdgeProperties > Graph; typedef graph_traits< Graph >::vertex_iterator Vit; Graph g(9); unsigned int i = 3; Vit vi; vi = vertex(i,g); ** I want vi to bi an iterator that points on the 3. vertex of the graph g. I attached the error message from g++ when compiling. Can anyone help?