Many initiatives designed to improve the quality of elementary and secondary teachers have been proposed and implemented at national, state, and local levels. It is unclear whether these initiatives are based on a common definition of teacher quality or adequate knowledge about the conditions that produce quality teaching. This article summarizes the results of a symposium of the National Research Council on the state of research knowledge on teacher quality. Topics for needed research that were identified in the symposium included studies on the effects of state and local policies which set new standards for teachers, studies on the subject-matter knowledge and preparation of teachers, analyses of alternative methods of developing teaching skills, and assessments of the effects of school conditions for teaching on career patterns of teachers.