To investigate the association between intake of freshwater fish and their fatty acids and the risk of breastcancer in Chinese women, we conducted a case-control study with 669 cases and 682 population-based controlsin Jiangsu Province of China. A structured questionnaire was used to elicit detailed information. Unconditionallogistic regression analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Totalfreshwater fish intake was linked to decrease in the adjusted OR for breast cancer, but without dose-dependence.Analyses by freshwater fish species showed that consumption of black carp and silver carp was inversely relatedto breast cancer risk, with adjusted-ORs for the highest intake category of black carp (≥500g/month) of 0.54(95%CI=0.33-0.92; P trend<0.002) and for silver carp (≥1000g/month) of 0.19 (95%CI=0.11-0.33; P trend<0.001).In contrast, consumption of crucian carp was positively related to breast cancer risk, with an adjusted OR forthe highest intake category (≥1000g/month) of 6.09 (95%CI=3.04-12.2; P trend<0.001). Moderate intakes of SFA,PUFA, n3-PUFA and n6-PUFA from freshwater fish may decrease the risk of breast cancer among premenopausalwomen. The findings of this study suggest that intake of freshwater fish and their fatty acids may modify risk ofbreast cancer, and that different species of freshwater fish could have a different actions on breast cancer risk.Future epidemiologic studies are needed to know the effects of freshwater fish intake on breast cancer risk andthe cause of these effects.