Because of their antioxidant and antimutagenic properties, flavonoids may reduce cancer risk. Some flavonoids have antiestrogenic effects that can inhibit the growth and proliferation of endometrial cancer cells. In order to examine the relation between dietary flavonoids and endometrial cancer, we analysed data from an Italian case-control study including 454 incident, histologically confirmed endometrial cancers and 908 hospital-based controls. Information was collected through a validated food-frequency questionnaire. We applied data on food and beverage composition to estimate the intake of flavanols, flavanones, flavonols, anthocyanidins, flavones, isoflavones, and proanthocyanidins. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated from multiple logistic regression models conditioned on age and study centre and adjusted for major confounding factors. Women in the highest quartile category of proanthocyanidins with ≥3 mers vs the first three quartile categories had an OR for endometrial cancer of 0.66 (95% CI=0.48-0.89). For no other class of flavonoids, a significant overall association was found. There was a suggestion of an inverse association for flavanones and isoflavones among women with body mass index <25 kg m(-2), and, for flavanones, among parous or non-users of hormone-replacement therapy women. High consumption of selected proanthocyanidins may reduce endometrial cancer risk.