Exposure to methylmercury, a developmental toxicant found primarily in fish. Fish is nutritionally important for providing long chain omega-3 fatty acids that are important for perinatal health. Since maternal transfer of mercury and omega-3 fatty acids are the primary routes for fetal (placental transfer) or infant (maternal milk) exposure, there is a critical need to develop specific advice for childbearing-aged women based upon the 2004 Dietary Guidelines Advisory Committee's recommended intake i.e., consume 8 ounces of fish per week. This clinical trial investigates whether weekly consumption of selected fish species for 12 weeks can improve plasma concentrations of the omega-3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) while reducing hair or blood mercury concentrations.