In Wisconsin, consumption of Great Lakes fish is an important source of exposure to polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), polybrominated diphenyl ethers (PBDEs), and other halogenated hydrocarbons, all of which may act as potential risk factors for breast cancer. We examined the association between sport-caught fish consumption and breast cancer incidence as part of an ongoing population-based case-control study. We identified breast cancer cases 20-69 years of age who were diagnosed in 1998-2000 (n = 1,481) from the Wisconsin Cancer Reporting System. Female controls of similar age were randomly selected from population lists (n = 1,301). Information about all sport-caught (Great Lakes and other lakes) fish consumption and breast cancer risk factors was obtained through telephone interviews. After adjustment for known and suspected risk factors, the relative risk of breast cancer for women who had recently consumed sport-caught fish was similar to women who had never eaten sport-caught fish [relative risk (RR) = 1.00; 95% confidence interval (CI), 0.86-1.17]. Frequency of consumption and location of sport-caught fish were not associated with an increased risk of breast cancer. Recent consumption of Great Lakes fish was not associated with postmenopausal breast cancer (RR = 0.78; 95% CI, 0.57-1.07), whereas risk associated with premenopausal breast cancer was elevated (RR = 1.70; 95% CI, 1.16-2.50). In this study we found no overall association between recent consumption of sport-caught fish and breast cancer, although there may be an increased breast cancer risk for subgroups of women who are young and/or premenopausal.