Background: This study is a systematic realist review to assess the benefits of Community-Based Participatory Research (CBPR) in health. Realist review is a relatively new methodology for reviewing complex interventions and programs. It holds the promise of generating knowledge about the context and mechanism features of interventions, which are not routinely assessed in reviews of experimental studies. We chose the approach because CBPR is complex, often difficult-to-measure, yet may play a significant role in determining research and health outcomes. The only previous systematic review of CBPR, commissioned by the Agency for Healthcare Research and Quality, failed to demonstrate a link between research outcomes and the participatory process. We hypothesize that this failure was due to a lack of fit between review methodology and the characteristics of community participation in research. In collaboration with leaders in the field of realist review and CBPR, our review design has been developed and tailored for assessing the evidence of participation, to ensure credibility and reliability of results, and to build theory for understanding the benefits of community-academic partnerships that underlie program outcomes. Objectives: To systematically review the benefits of CBPR using a realist review approach. Methods: Key concepts in realist review methodology will be described and exemplified. These include: middle-range theory, demi-regularities, and context-mechanism-outcome (CMO) configuring. Results and Conclusion: Twenty-six sets of CBPR health interventions are currently being synthesized. The methodology, methods and preliminary results will be reported as well as insights gained from conducting a realist review for this large, heterogeneous, and complex body of literature.