The relation between diet and endometrial cancer was examined in a population-based case-control study conducted in Shanghai, People's Republic of China, between 1988 and 1990, involving interviews with 268 cases and 268 controls aged 18-74 years. The subjects' usual dietary intake of 63 major foods during the previous 10 years (disregarding any recent changes) was measured by means of a structured quantitative food questionnaire. Although women in the highest quartile of total caloric intake had a 2.1-fold increased risk of endometrial cancer, risk varied according to the source of calories. The highest quartiles of caloric intake from fat and protein were associated with odds ratios of 3.9 and 3.1, respectively, while calories from carbohydrates, the major contributor of total calories in this population, were not related to risk. The association of fat and protein with endometrial cancer risk was confined to foods of animal origin in the diet. After adjustment for age, body mass index (weight (kg)/height (m)2), and number of pregnancies, odds ratios were 3.5 (95% confidence interval (CI) 2.0-6.0) and 3.0 (95% CI 1.7-5.1) for women in the highest quartiles of intake of animal fat and animal protein, respectively. Food group analyses showed a similar pattern, with high consumption of meat, eggs, and fresh fish being associated with elevated risks. After adjustment for total calories, no significant association of risk was found with intake of vegetables or dark green/yellow vegetables, or with estimated carotene intake, although fruit and allium vegetables were associated with some reduction in risk. These results suggest that diets rich in animal fat and animal protein may play an important role in the etiology of endometrial cancer.