The purpose of this study was to describe what federally funded teacher enhancement looks like at its best and to determine whether best practice can be recognized as such by professionals in the field. Narrative descriptions of programs were analyzed for strength of evidence supporting key elements of best practice. Other data collection methods included surveys, telephone interviews with participants, analysis of teacher logs, and in-depth case studies. Four key elements of best practice were articulated: instructional approach, immersion in science, systemic approach, and follow-up. Three themes that ran consistently through the best institutes were: a thematic approach, supportive infrastructure, and sophisticated use of evaluation data. This study indicated that teacher enhancement provided by the federal agencies included in the study has much to offer teachers as individual professionals and much to contribute to educational reform efforts. As a group, the institutes promoted and modeled a hands-on/minds-on, constructivist approach to instruction, immersed teachers in the practice of science, and facilitated transfer of learning with follow-up support throughout the school year. Institute profiles, characteristics of participants, characteristics of institutes, coding methodology, and best-practice rating of individual institutes are included in five appendices. (JRH)