The authors claim that the principal contribution of research on teacher thinking is enrichment of understanding of what teachers know and what teaching entails. Studies of teacher planning, decision making, knowledge, and theorizing can be used to provide prospective teachers with a realistically complex picture of the cognitive aspects of teaching. This research also supports the development of a conception of teaching as a reflectively professional enterprise. For both novices and experienced teachers the proposed goals of applying this research are to promote understanding of teaching as a design profession and to empower teachers in self-directed professional development efforts. Knowledge about how teachers get their work done is of worth to teachers not because it will provide them with new tools to use, but rather because it changes the way researchers view what teachers need to know; researchers can then be of more help to teachers. Descriptions of teaching that have been produced by studies of teacher thinking can help to provide a framework for researchers to decide what sorts of information, advice, and support will be useable in the classroom. (Author/JD)