Consistent with the conception of teaching as a learning profession, the authors' vision of a professional teacher workforce is one in which teachers do take responsibility for their own learning--their work. Supporting teachers' transition from workers to learners may require learning opportunities of a different type--work opportunities offered for learning's sake rather than learning opportunities provided for work's sake. To trace the evolution of teachers as learners, the authors examine past and current staff development practices in light of their new vision of "profession" development, in which teachers' knowledge-seeking goals are valued and supported and their work affords them opportunities to achieve their goals. In this chapter, the authors explore the difference between staff development opportunities typically offered to "schools of teachers" and learning opportunities that situate teaching in a broader professional context. They examine the theories of learning and teacher knowledge that may explain these differences, and review promising new practices such as teacher research in which teachers work together within and across schools to contribute to the professional knowledge base and the improvement of the teaching profession.