Dear all, Sorry for the newbie question! Given the index of a vertex, how can I get its descriptor? I guess function vertex (page 225 of The Boost Graph Library) does that but the function is not defined. In fact, what I want to do is to check whether an edge belongs to a graph in a context where descriptors get invalidated after vertex removals? Suppose I have done this: // create a typedef for the Graph type typedef adjacency_list<vecS, vecS, bidirectionalS> Graph; // Make convenient labels for the vertices enum { A, B, C, D, E, N }; const int num_vertices = N; const char* name = "ABCDE"; // writing out the edges in the graph typedef std::pair<int, int> Edge; Edge edge_array[] = { Edge(A,B), Edge(A,D), Edge(C,A), Edge(D,C), Edge(C,E), Edge(B,D), Edge(D,E) }; const int num_edges = sizeof(edge_array)/sizeof(edge_array[0]); // declare a graph object Graph g(num_vertices); Then I remove some vertices. Now I want to check whether edge <A,B> is still there. Calling edge(A,B,g) would not be OK because the descriptors are no longer referring to the same vertices.... Thanks in advance for your answer, Luis