Researchers posit that teachers' teaching and learning are improved by teachers' collective efforts to examine and reflect on practice. Yet the questions of what and how teachers learn when collaborating with colleagues remain unanswered: What kinds of knowledge and skills do teachers acquire in conjunction with their collaboration? What brings about teachers' learning when they collaborate in teams? And how does their learning affect their practice? In this paper I will examine to what extent action learning can contribute to answering these questions from a Danish perspective. I begin the paper by presenting action learning, which formed the framework for the teacher team collaboration that provides the empirical fundament of this paper, and by discussing my roles as consultant and researcher. Thereafter, first the possibilities, then the limitations of teachers' collaboration in teams for learning are discussed. Finally, several methodological dilemmas are considered and the paper's conclusions are presented. (Contains 1 note.)