This article describes an empirical exploration of three initiatives in which teachers in secondary education (learn to) research their own practice in collaboration with university-based research institutes, aiming at professional development and knowledge construction. We found evidence of professional development, mainly at the level of the individual teacher and to a lesser extent at the school level. Teachers reported that they developed their knowledge and skills with respect to doing research, as well as a more critical attitude, and consciousness of and intentions to change teaching performance. Organisational conditions appeared to be related to results at school level. The article concludes by stating that, if teacher research is to lead to the collaborative development of more scientifically accepted knowledge, greater attention will need to be paid to the dissemination of knowledge as well as to the quality assurance of the research performed. (Contains 3 tables.)