Despite the established role of obesity in the etiology of endometrial cancer, limited data are available from analytical epidemiologic studies on the association of risk with dietary factors. A case-control study of 399 cases and 296 controls conducted in five areas of the United States from 1 June 1987 to 15 May 1990, enabled evaluation of risk related to dietary intakes adjusted for potential confounders. Caloric intake was associated modestly with increased risk (odds ratio [OR] = 1.5, 95 percent confidence interval [CI] = 0.9-2.5 for highest cf lowest quartiles of intake), with the principal contributors being fat and protein calories. After adjustment for other risk factors, including body mass, increased risk was associated with higher intakes of fat. Several components of fat investigated were associated with increased risk, although associations were slightly stronger for saturated fat (OR = 2.1, CI = 1.2-3.7) and oleic acid (OR = 2.2, CI = 1.2-4.0) than for linoleic acid (OR = 1.6, CI = 0.9-2.8). Food-group analyses showed intake of complex carbohydrates--and specifically of breads and cereals--associated with reduced risks (OR = 0.6, CI = 0.4-1.1), whereas animal fat and fried foods were associated with elevated risks (OR = 1.5 and 1.7, respectively). The relations of endometrial cancer with animal fat and complex carbohydrates were independent. No consistent associations were noted for intakes of cholesterol, fiber, vitamins A and C, individual carotenoids, or folate-rich foods. These data imply an etiologic role for a diet rich in total fat and/or animal fat and low in complex carbohydrates with endometrial cancer.(ABSTRACT TRUNCATED AT 250 WORDS)