Introduction: Tribal members concerned about health risks to residents of all ages from water contamination initiated this project. Our community-based risk assessment examines exposures to contaminants via domestic, cultural and recreational water uses on the Crow Reservation. Our hypotheses are that: reliance on shallow wells, subsistence fishing, traditional uses of river water and other practices place residents at an increased risk of exposure to environmental contaminants via water sources; and following Community Based Participatory Research principles in conducting risk assessment, communication and mitigation is an effective way to reduce health disparities in underserved communities. Methods: Our partnership includes the local Tribal College, the Crow Tribe, the Indian Health Service Hospital, the Apsaalooke Water and Wastewater Authority, the Tribal Elders Committee, Montana State University Bozeman and the University of New England. The partners guide the work through monthly Steering Committee meetings. We are conducting: (1) bacterial and chemical analyses of multiple water sources, (2) mercury analyses of local fish, (3) family surveys to assess routes of exposure and (4) interviews with key informants. Additionally, we're utilizing unpublished data, multivariate analysis and GIS. Tribal College science majors are our research interns, building community capacity. Results/Conclusion: The community has used the data to obtain funding to upgrade the water and wastewater treatment systems. Mitigation strategies are being piloted. The resulting holistic risk assessment is innovative in utilizing mixed methods and incorporating both physiological and non-physiological health risks grounded in the cultural significance of water and local economics. Community and university partners will co-present.