The primary mission of NASA's Global Change Master Directory is to provide access to earth sciences data sets, data services, collaborations, and conferences, but it also includes life sciences data sources, with emphasis on those relating to climate change and ecology. Links to and descriptions of more than 19,000 data sets and data ervices are included. Results can be obtained by choosing one of the main topic areas or by using the available keyword search, and can be refined by keyword or category. Special features include a means for scientists working on research on global change to share information by uploading their own data sets or services descriptions and a user discussion list for participating in discussions on GCMD metadata and access consideration. GCMD provides special access for students through The Learning Center, which selects data and services of particular potential interest and provides illustrations and descriptions designed to appeal to students.