INTRODUCTION: Alcohol consumption is a well-established risk factor for breast cancer. Some studies have suggested that the risk of breast cancer associated with alcohol consumption is greater for women with a history of benign breast disease (BBD). We hypothesized that among women with biopsy-confirmed BBD, recent alcohol consumption would increase the risk of breast cancer in women with proliferative breast disease to a greater extent than in women with nonproliferative breast disease. METHODS: We conducted a nested case-control study in the Nurses' Health Study I and II. The cases (n = 282) were women diagnosed with incident breast cancer, with a prior biopsy-confirmed breast disease. The controls (n = 1,223) were participants with a previous BBD biopsy, but without a diagnosis of breast cancer. Pathologists reviewed benign breast biopsy slides in a blinded fashion and classified the BBD as nonproliferative, proliferative without atypia, or atypical hyperplasia, according to standard criteria. RESULTS: Women with nonproliferative breast disease consuming > or = 15 g of alcohol per day had a nonsignificant 67% increased risk of breast cancer (odds ratio = 1.67; 95% confidence interval 0.65 to 4.34) compared with nondrinkers. There was no evidence that recent alcohol consumption increased the risk of breast cancer to a greater extent in women with proliferative BBD than among women with nonproliferative BBD (P for interactio n = 0.20). CONCLUSION: Contrary to our a priori hypothesis, there was no evidence that recent alcohol consumption increased the risk of breast cancer to a greater extent among women with proliferative BBD than among women with nonproliferative BBD.