This paper reviews significant literature on teachers' beliefs, offers support for the contention that current research is moving in a more utilitarian direction than in the past, and argues that continuing research into teachers' beliefs could be useful in improving teaching practice. The review focuses on five areas: (1) the different ways that teachers' beliefs have been defined and described; (2) the methodologies used to examine the beliefs of teachers; (3) the nature of the beliefs that teachers hold; (4) the relationship between what teachers believe and what they do; and (5) the attempt to define a teacher-effectiveness dimension based on the beliefs that teachers hold (or do not hold). The examination indicates that research is needed to clarify how a knowledge of teachers' beliefs can improve their practice; a methodology appropriate to such questions is suggested. The paper concludes with a discussion of how current knowledge of the relationships between teachers' beliefs and practices can inform inservice and preservice education. A bibliography is included. (TE)