Although most data support an overall relation of alcohol consumption with risk of breast cancer, the timing of alcohol consumption as it relates to risk of breast cancer is still debatable. The authors examined this issue in a case-control study conducted among non-Hispanic white and Hispanic women in Los Angeles. Cases aged 55-64 years at diagnosis in 1987-1989 were enrolled through the Cancer Surveillance Program of Los Angeles County (a Surveillance, Epidemiology, and End Results Program registry). Community controls were individually matched to cases by age (+/- 3 years), ethnicity, and neighborhood. In-person interviews were completed with 1510 matched pairs, of which 1431 met the inclusion criteria for the present analysis. In a multivariate conditional logistic regression model that simultaneously included terms for alcohol consumption at age 25 years, age 40 years, and in the recent past, clear differences among the age-specific associations were not observed, and the results suggested associations were not observed, and the results suggested that intake at each time independently contributed to risk. The odds ratios associated with estimated average lifetime intake were: for <6 g/day, 1.01; for 6-11 g/day, 1.21; for 12-18 g/day, 0.94; for 19-32 g/day, 1.63; for 33-45 g/day, 2.45 and for > or = 46 g/day, 0.94 compared with abstainers (P for trend = 0.01). Use of estrogen replacement therapy did not modify the risk associated with alcohol consumption, in contrast with the findings in two previous studies. This large study supports a relation between risk of breast cancer and alcohol consumption and suggests that lifetime intake may be the best indicator of alcohol-associated risk.