||An increased risk of renal cell carcinoma (RCC) has been linked with obesity. However, there is limited information about the contribution of dietary fat and fat-related food groups to RCC risk. A population-based case-control study of 406 cases and 2434 controls aged 40-85 years was conducted in Iowa (1986-89). For 323 cases and 1820 controls from the present study, information on dietary intake from foods high in fat nutrients and other lifestyle factors was obtained using a mailed questionnaire. Cancer risks were estimated by OR and 95 % CI, adjusting for age, sex, smoking, obesity, hypertension, physical activity, alcohol and vegetable intake and tea and coffee consumption. In all nutrient analyses, energy density estimates were used. Dietary nutrient intake of animal fat, saturated fat, oleic acid and cholesterol was associated with an elevated risk of RCC (OR = 1.9, 95 % CI 1.3, 2.9, P trend < 0.001; OR = 2.6, 95 % CI 1.6, 4.0, P trend < 0.001; OR = 1.9, 95 % CI 1.2, 2.9, P trend = 0.01; OR = 1.9, 95 % CI 1.3, 2.8, P trend = 0.006, respectively, for the top quartile compared with the bottom quartile of intake). Increased risks were also associated with high-fat spreads, red and cured meats and dairy products (OR = 2.0, 95 % CI 1.4, 3.0, P trend = 0.001; OR = 1.7, 95 % CI 1.0, 2.2, P trend = 0.01; OR = 1.8, 95 % CI 1.2, 2.7, P trend = 0.02; OR = 1.6, 95 % CI 1.1, 2.3, P trend = 0.02, respectively). In both the food groups and nutrients, there was a significant dose-response with increased intake. Our data also indicated that the association of RCC with high-fat spreads may be stronger among individuals with hypertension. These findings deserve further investigation in prospective studies.