This study investigates how pre-service and in-service teachers participate in an online community for learning to teach. Members' levels and patterns of participation and social interaction were examined via social network analysis of activity logs and content analysis of interviews. The results of the analyses show that (a) members' levels and patterns of participation varied across time, member types, and tools; (b) members' identity and levels of participation were reciprocally associated; (c) there were similarities and differences in members' usage of computer-mediated communication (CMC) tools; (d) members showed growth in their knowledge and skills for teaching via mutual engagement, creating joint enterprise, and establishing shared repertoire supported by CMC tools; and (e) lack of time influences members' levels of participation. (Contains 9 tables and 10 figures.)