Alcohol consumption is associated with a moderate increase in breast cancer risk, possibly because alcohol increases estrogen levels in blood. Certain types of breast carcinomas are more hormonally responsive than others, including those that have a lobular histology or are hormone receptor positive, but few studies evaluating alcohol use and breast cancer risk have stratified results by histology or estrogen receptor (ER)/progesterone receptor (PR) status. We conducted a population-based case-control study of women 65-79 years of age in western Washington State. Women (975) diagnosed with invasive breast cancer during 1997-1999 were compared with 1007 controls. Ever-use of alcohol over the past 20 years was associated with a 1.3-fold [95% confidence interval (CI), 1.0-1.5] increased risk of breast cancer, although this increase was primarily limited to women who consumed > or =30.0 g/day of alcohol [odds ratio (OR), 1.7; 95% CI, 1.1-2.6]. Differences in risk by histology were observed: ever-use of alcohol was associated with a 1.8-fold (95% CI, 1.3-2.5) increased risk of lobular cancer but only a 1.2-fold (95% CI, 0.9-1.4) increased risk of ductal cancer. Ever-users of alcohol had an increase in risk of ER+/PR+ tumors (OR, 1.3; 95% CI, 1.1-1.7), but no change in their risks of ER+/PR- or ER-/PR- tumors. Alcohol use appears to be more strongly associated with risk of lobular carcinomas and hormone receptor-positive tumors than it is with other types of breast cancer. These results are consistent with there being an underlying hormonal basis for the known association between alcohol use and breast cancer incidence.