A framework for thinking about teacher assessment is provided. Good teaching is characterized and target domains for teacher assessment are identified. A number of challenges to existing assessment practices and plans for future assessment practices are identified. New systems of teacher assessment should be designed to triangulate across domains of teacher knowledge, skills and beliefs; teachers' classroom behaviors; and student outcomes. Since an ideal system of teacher assessment will almost surely exceed available resources of knowledge and effort, the costs and benefits of implementing teacher assessment practices must be evaluated to see if the expense is worth the results and to guard against undesirable side effects, such as elimination of minority teachers from the teacher corps. (Author)