In many studies, moderate alcohol consumption has been associated with increases in the risk of breast cancer of about 50-100%. The authors examined recent alcoholic beverage consumption in relation to the risk of breast cancer in a case-control study of women aged less than 70 years, conducted in Toronto, Ontario, Canada, from 1982 to 1986: 607 breast cancer cases identified in a cancer hospital were compared with 1,214 controls matched to the cases on neighborhood and decade of age. The subjects were interviewed at home. Confounding factors were controlled by conditional logistic regression. The relative risk estimates for women who consumed alcohol, relative to women who drank less than one alcoholic beverage (drink) per month, were close to 1.0: for women who drank at least one alcoholic beverage per day, the multivariate estimate was 0.9 (95% confidence interval 0.6-1.2). Among subgroups of women, including those at low baseline risk, there was also no association. For a subset of cases compared with hospital controls, once again there was no association. The relative risk (RR) estimate was elevated for women who drank at least one beer daily (RR = 1.7) and reduced for women who drank at least one glass of wine daily (RR = 0.7), but neither estimate was statistically significant. The results suggest that recent alcohol consumption does not influence the risk of breast cancer. Selection bias cannot be ruled out, however. In addition, because determinants of alcohol use are not well understood, control of confounding may have been incomplete in the present study and in other observational studies of alcohol and breast cancer.