Hi, I'm not sure whether to post here or create a new thread. But since your topic is very similar to my question, I'll post it here. I have been using listS for both edges and vertices with adjacency_list. According to the online documentation of BGL, clear_vertex() should not invalidate the adjacency_iterator in this case. However, in my code that's exactly what happens: I call adjacent_vertices() on a vertex A, which gives me an adjacency_iterator. Then I remove all edges from A by calling clear_vertex(). Then I want to use the adjacency_iterator obtained previously to check the new degrees of all (previous) neighbours of the removed vertex v. But the program crashes with a segmentation fault, when I try to use the iterator. Has anyone experienced this before? Or do you have any ideas how to make it work? Cheers, Silvia