This paper offers a conceptual framework for establishing a science of transdisciplinary action research. Lewin's (1951) concept of action research highlights the scientific and societal value of translating psychological research into community problem-solving strategies. Implicit in Lewin's formulation is the importance of achieving effective collaboration among behavioral researchers, community members and policy makers. The present analysis builds on Lewin's analysis by outlining programmatic directions for the scientific study of transdisciplinary research and community action. Three types of collaboration, and the contextual circumstances that facilitate or hinder them, are examined: (1) collaboration among scholars representing different disciplines; (2) collaboration among researchers from multiple fields and community practitioners representing diverse professional and lay perspectives; and (3) collaboration among community organizations across local, state, national, and international levels. In the present analysis, transdisciplinary action research is viewed as a topic of scientific study in its own right to achieve a more complete understanding of prior collaborations and to identify strategies for refining and sustaining future collaborations (and their intended outcomes) among researchers, community members and organizations.