The hypothesis has been raised that coffee consumption may increase the incidence of breast cancer, based on the report that fibrocystic breast disease, a risk factor for breast cancer, regresses after abstention from coffee and other methylxanthines. The relation between recent coffee consumption and the risk of breast cancer was evaluated in a case-control study, based on interviews conducted 1975–1982 at several mainly eastern US teaching and community hospitals. The responses of 2,651 women with newly diagnosed breast cancer were compared with those of 1,501 controls with nonmalignant conditions and 385 controls with cancers at other sites. The relative risk estimates for levels of coffee drinking up to seven or more cups daily, relative to none, approximated 1.0 with narrow 95% confidence intervals. After allowance for confounding, the relative risk estimate for drinking at least five cups a day was 1.2 (95% confidence interval, 0.9–1.6) using the noncancer controls and 1.1 (0.7–1.6) using the cancer controls. Coffee consumption was not associated with an increase in the risk of breast cancer among women with a history of fibrocystic breast disease, nor were tea or decaffeinated coffee associated with an increase in the risk of breast cancer. The results suggest that the recent consumption of coffee does not influence the incidence of breast cancer.