A community of practice (CoP) is an organizational form that promotes sense making, knowledge management, and learning. It is important to understand how and why these communities form and grow over time. These questions are explored in a qualitative analysis of a knowledge management (KM) community of practice. This case study includes a description of how the organization formed, survived, grew, and matured over a five-year period (1999-2004). Several practices and structures related to CoP development are identified: operations, roles and responsibilities, communications, subgroup structures, use of information technologies, and other aspects of organizing. Using data from several sources (e.g., membership surveys, interviews with key informants, document analysis), four sets of critical success factors are identified: Individual factors, content factors, meeting factors, and organizational factors. These factors are arranged into a descriptive model of the function and structure of CoPs over the life cycle. This work also sheds light on how to set up and successfully grow a community of practice.