We examined the reliability of self-reported alcohol consumption in past age periods of women's lives. As part of a case-control study of breast cancer conducted in Massachusetts and Wisconsin in 1988-1991, the same questionnaire was administered for a second time to 211 controls (mean age = 54 years) after an interval of 6-12 months. The Spearman correlation coefficients between the average number of grams of alcohol consumed daily reported in the two interviews, by age period of consumption, were: 16-19 years, r = 0.81; 20-29 years, r = 0.84; 30-39 years, r = 0.75; and for recent consumption, r = 0.77. Self-reported alcohol consumption throughout adult life was reported with precision sufficient to make the ranking of subjects' intake consistent between interviews.