This research project is creating and evaluating multi-user virtual environments (MUVEs) that use digitized museum resources to enhance middle school students' motivation and learning about science and its impacts on society. MUVEs enable multiple simultaneous participants to access virtual architectures configured for learning, to interact with digital artifacts, to represent themselves through graphical "avatars," to communicate both with other participants and with computer-based agents, and to enact collaborative activities of various types. The project's educational environments are extending current MUVE capabilities in order to study the science learning potential of interactive virtual museum exhibits and participatory historical situations in science units using the NSF-funded Multimedia and Thinking Skills (MMTS) program, an inquiry-centered curriculum engine. George Mason University's (GMU) Virtual Environments Lab, the Division of Information Technology and Society in the Smithsonian's National Museum of American History (NMAH), and pilot teachers from the Gunston Middle School in Arlington, Virginia are co-designing these MUVEs and implementing them in a variety of middle school settings. In particular, this project is studying how the design characteristics of these learning experiences affect students' motivation and educational outcomes, as well as the extent to which digitized museum can aid pupils' performance on assessments related to national science standards. This research also is examining both the process needed to successfully implement MMTS-based MUVEs in typical classroom settings and ways to enable strong learning outcomes across a wide range of individual student characteristics.