The role of communities of practice in knowledge creation is recognized in a number of contexts. The authors take a socio-technical perspective and identify four characteristics of such communities: situated learning, situated action, distributed cognition and social infrastructure. These are combined into a loosely normative framework to define and analyze communities of practice at the level of online micro-organization. The framework is applied to three development projects: a reference service, a virtual enterprise initiative and a simulation of an electronic shopping mall. The authors discuss its potential in explaining and stimulating new knowledge in micro-level online work environments.