The term "teacher enhancement" is recent; however, its underlying goal--to improve, broaden, and deepen the disciplinary and pedagogical knowledge of elementary and secondary teachers employed in public schools--has been addressed by educators and educational policymakers in the past, usually through the mechanism of inservice training. This report presents a perspective on teacher enhancement programs over the last four decades. Chapters include: (1) "Historical Perspectives on Current Teacher Enhancement Programs in Science and Mathematics" covering the period before the 1950s to the 1990s; (2) "Current Teacher Development/Enhancement Programs in Science and Mathematics"; and (3) "What Evaluations Tell Us about the Impact of Teacher Enhancement Programs". Appendices include lists of teacher enhancement programs and teacher enhancement programs with evaluation components. (JRH)