The past two decades have witnessed a surge of interest and investment in transdisciplinary scientific teams and centers. Only recently, however, have efforts been made to evaluate the collaborative processes, and the scientific and public policy outcomes, of these endeavors. This presentation offers a conceptual framework for understanding and evaluating transdisciplinary research and describes a large-scale national initiative - the Transdisciplinary Tobacco Use Research Centers (TTURCs) - undertaken to promote cross-disciplinary collaboration in tobacco science and control. A five-year evaluation of collaborative processes and outcomes observed across multiple TTURCs suggests key factors that influence the effectiveness of collaborative research spanning diverse fields. Implications of this study for developing and evaluating transdisciplinary research and community interventions to promote higher levels of physical activity in the population are discussed.