Hi, Below is a list of bugs (at least I think so) in boost graph library: 1. I used the functions illustrated in file "components_on_edgelist.cpp" on a adjacency_list graph instead of a edge_list graph. It gave the correct number of components in the graph, but when printing out each components, the nodes in some of the components were disconnected. Also, segmentation fault was flagged.(This happened when the graph had a lot of components.) 2. I ran the source code in file "subgraph.cpp" as it was, the output was different from the sample output given in the same file. The difference was: the subgraph had global edge index, but local vertex index. 3. When creating multiple subgraphs, code like below would give segmentation fault: " typedef property VertexName; typedef property VertexProperty; typedef property EdgeProperty; typedef subgraph< adjacency_list > Graph; ... Graph G(N); //add edges to G //assign names to vertices in G ... Graph & G1 = G.creat_subgraph(); //add vertices to G1 //assign names to vertices in G1 ... " When using function put(PropertyTag, const subgraph& g, Key k_local, const Value& value) to assign names to the vertices of subgraph G1(it seems that the name of vertices in G is not automatically inherited by G1.), it gave segmentation fault. This problem would not happen if the number of subgraphs was few such as 2. I found the above problems when I tried to create subgraphs for each component in the graph when the number of components was large. Thanks for your time, Qiaofeng