This study examined the association between coffee consumption and the risk of endometrial endometrioid adenocarcinoma (EEA) in Japan by a case-control design. The cases consisted of 107 women less than 80 years of age from two medical centers who had been histopathologically diagnosed to have EEA. The controls, selected from the participants of a cancer-screening program, were 214 women, with two controls selected for each case (matched for age and for area of residence). A self-administered questionnaire containing questions to determine dietary and beverage consumption, as well as reproductive history, was distributed to the cases and controls. Conditional logistic regression analysis was used to estimate the odds ratio (OR) of EEA for three levels of coffee consumption with adjustment for potential confounding factors. The multivariate-adjusted OR of EEA for individuals in the highest tertile of coffee consumption (2 to 3 cups or more/day) was 0.4 [95% confidence interval (CI), 0.2-0.9], and that of cases in the intermediate tertile (5 to 6 times/week-1 cup/day) was 0.6 (95% CI, 0.3-1.2), relative to the individuals in the lowest tertile of coffee consumption (3 to 4 times or less/week) (P for trend=0.014). The above association was observed in postmenopausal women (P for trend=0.016), but not in premenopausal women (P for trend=0.90). This study thus revealed an inverse dose-response relationship between coffee consumption and the risk of EEA, and its strong association in postmenopausal women but not in premenopausal women.