Teachers in secondary education mainly feel responsibility for their own classroom practice, resulting in largely autonomous and isolated work and private learning activities. Most teachers teach separate classes behind closed doors and learn about teaching by teaching, often described as trial and error (Hodkinson and Hodkinson in Stud Continuing Educ 25:3-21, 2003; Int J Train Dev 8: 21-31, 2004). Moreover, teacher professional development has mostly taken place outside school, thus removing teacher learning from the workplace (McMahon in Educational management: redefining theory, policy and practice. Paul Chapman Publishing, London, pp 102-113, 1999). From the perspective of the development of collective capacity of schools, this is not a desirable situation. Teachers need to share their teaching practice and learning experiences in order to stimulate a learning culture in schools. In their work on communities of practice and school teachers' workplace learning, Hodkinson and Hodkinson (Stud Continuing Educ 25:3-21, 2003; Int J Train Dev 8: 21-31, 2004) conclude that a highly collaborative working culture is accompanied by a learning culture. Teachers learned from one another intuitively, as an ongoing part of their practice. They were happy to move in and out of one another's lesson, seeing the work that was going on. There are steadily expanding claims that teacher communities contribute to teacher development, the collective capacity of schools and improvements in the practices of teaching and schooling. Teacher community can be understood as a way to bring teachers together to share their knowledge and practices. As such, a community of teachers can be seen to offer an environment for teachers' learning. However, there seems to be no consensus on the definition and indicators of teacher communities, which are conditional for measuring teacher communities. In this article, we aim at the development of a descriptive model involving a definition, indicators and formation of teacher communities in secondary education in the Netherlands, shared by both practitioners and researchers in the field.