Implementation of evidence-based HIV/STD prevention interventions can play an important role in reducing HIV and sexually transmitted diseases. This article describes the development, implementation, and lessons learned of the Diffusion of Effective Behavioral Interventions (DEBI) project, a strategy funded by the Centers for Disease Control and Prevention to diffuse evidence-based, group- and community-level HIV/STD prevention interventions to health departments and community-based organizations nationwide. The article specifically provides an overview of the rationale, description, and theoretical foundation of the project; a review of marketing efforts, including assessment of interests, needs, and capacities relative to the project; a description of project products, their purpose, approach employed to develop them, and their use by implementers; a description of the project's training coordination functions and activities; technical assistance issues; an overview of process and outcome evaluation components; new developments in response to feedback; and a discussion of future directions for DEBI. Project successes and challenges are addressed to inform future efforts to diffuse prevention interventions.