A fundamental component of community-based health promotion efforts to eliminate disparities is the mobilization of community involvement to address not only individual but also systemic and political causes of inequalities in health. The participatory action research (PAR) paradigm is well suited to address these multilevel inequalities in research and evaluation experienced by many ethnic and racial communities. In this article, a case study of a project to reduce health disparities in breast and cervical cancer among seven Southeast Asian and Pacific Islander communities in Southern California is presented. The authors applied a PAR framework to the process of needs assessment and program planning to understand and address the complex and multilevel factors that contribute to the problem of disparate breast and cervical cancer screening rates in these communities. Finally, the authors describe the lessons that were learned about how to promote collaborative research as an essential element in the design of projects and studies to address ethnic disparities in health outcomes for breast and cervical cancer.