In a multicenter case-control study that included 400 cases and 297 controls, we examined the relation of moderate alcohol consumption to risk of endometrial cancer. We estimated average weekly intake of alcohol during adulthood from the reported frequency of intake of beer, wine, and liquor. The relative risk of endometrial cancer was 0.82 (95% confidence interval = 0.6-1.2) among women who drank, compared with lifelong abstainers. The weak protective effect of alcohol was due to a stronger inverse association among young women (< 55 years). In young women, the age-adjusted relative risks for three levels of drinking ( < 1, 1-4, > 4 drinks per week), from lowest to highest, were 0.78, 0.64, and 0.41 compared with nondrinkers. The risk estimates were not materially altered after adjustment for a variety of factors related to alcohol intake and to low risk of the disease (for example, smoking, oral contraceptive use, low body mass index, increased physical activity). The protective effect of alcohol could not be attributed to one particular type of alcohol-containing beverage, but beer appeared to have the most pronounced effect. These results suggest an inverse association between moderate alcohol consumption and endometrial cancer risk among young women, but support for a causal association is qualified and requires confirmation.