To address disproportionately high rates of diabetes morbidity and mortality in some of Chicago's medically underserved minority neighborhoods, a group of community residents, medical and social service providers, and a local university founded the Chicago Southeast Diabetes Community Action Coalition, a Centers for Disease Control and Prevention REACH 2010 Initiative. A community-based participatory action research model guided coalition activities from conceptualization through implementation. Capacity building activities included training on: diabetes, coalition building, research methods, and action planning. Other activities sought to increase coalition members' understanding of the social causes and potential solutions for health disparities related to diabetes. Trained coalition members conducted epidemiologic analyses, focus groups, a telephone survey, and a community inventory. All coalition members participated in decisions. The participatory process led to increased awareness of the complexities of diabetes in the community and to a state of readiness for social action. Data documented disparities in diabetes. The participatory action research approach (a) encouraged key stakeholders outside of the health care sector to participate (e.g., business sector, church groups); (b) permitted an examination of the sociopolitical context affecting the health of the community; (c) provided an opportunity to focus on preventing the onset of diabetes and its complications; (d) increased understanding of the importance of community research in catalyzing social action aimed at community and systems change and change among change agents.