If the true efficacy of preservice programs in the overall development of science teachers is to be accurately assessed, researchers and practitioners must work toward establishing a solid research base that critically examines the linkages between teacher preparation, classroom instruction, and pupil learning, to act as a lens to guide practice and feed information back into existing teacher education programs to improve their quality. The U.S. NSF-funded IMPPACT Project represents a multi-university, collaborative research study that was developed in response to the need for empirical evidence regarding the efficacy of science teacher preparation programs. The purposes of this longitudinal, mixed methods study were to: 1) better understand secondary science teachers' learning of content and pedagogy over time as a result of key interventions within these preparation programs; 2) assess the subsequent impact of this learning on their classroom teaching and student achievement; and 3) determine what factors significantly influenced these teachers' beliefs and classroom practices following graduation. Interdisciplinary research teams at each university were responsible for collection and analysis of data, while a panel of experts provided the research team with technical assistance. Key research findings and their implications for preservice teacher education programs are highlighted.