This paper proposes knowledge map creation and maintenance approaches by utilizing information retrieval and data mining techniques to facilitate knowledge management in virtual communities of practice. Besides evaluating their performance using synthesized data, the generated knowledge maps for documents collected from the teachers? cyber community, SCTNet, and the master thesis repository at Taiwan?s National Central Library, are evaluated by domain experts. Domain experts are asked to revise the obtained knowledge maps, and the proportion of modification is small and acceptable. Therefore, the developed approaches are suitable for support knowledge management of professional communities on the Internet.