Recent reform efforts in preservice teacher education have promoted the concept of preservice teacher cohorts. Cohorts may serve to develop a greater sense of community and also facilitate an improved understanding of the connections between university studies and school practice. This monograph examines the potential ability of preservice teacher cohorts to improve the preparation of preservice teachers in mathematics and science. Research on cohorts that include mathematics- and/or science-focused cohorts is summarized. While some progress is apparent, there are many areas in mathematics and science preparation that are largely unaffected by the new structure. There may also be effects that are undesirable. Both the literature and the site visits highlight the need for program developers to attend to both design and purpose. It is concluded that more research is needed to document the effects of preservice cohorts on teacher preparation. (Author/KHR)