While there has been a trend toward greater disciplinary collaboration over the last several decades, the emergence of the HIV pandemic has required that disciplines work more closely and creatively to generate the multiple and innovative approaches necessary to meet the demands for effective prevention and treatment. This paper describes the nature of collaborative relationships among U.S. and Indian anthropologists, psychologists, demographers, epidemiologists, physicians and representatives of other fields and sectors in conducting a large scale, multi-year HIV/STD prevention project directed toward married men in urban poor communities in Mumbai (Bombay), India. The project has challenged members of the participating disciplines to develop a transdisciplinary conceptual model, to test the model with community-based formative research and to utilize the results in the development and implementation of a multi-level (community, provider and patient) intervention. The paper describes the interaction among disciplines and international sectors in the conceptualization, methodology and community-based action components of the project. In addition, it examines both the inhibiting and facilitating factors that are a part of the collaborative process. The paper concludes with implications for future transdisciplinary partnerships.