The role of diet in the aetiology of renal cell carcinoma was investigated in a population-based case-control study in Denmark. Cases were 20-79 years old, with a histologically verified diagnosis of renal cell carcinoma. Controls were sampled from the general population and were frequency-matched on age and sex. A total of 351 cases (73% of the eligible) and 340 controls (68% of the eligible) were included in the study. Dietary information was obtained in a self-administered food frequency questionnaire and the information was confirmed in a subsequent interview performed by trained interviewers who also elicited information on other suspected risk factors such as smoking, occupation, medical history, education and reproductive history. Logistic regression models were used to calculate the odds ratios, and, both frequency of consumption of various food stuffs and computed nutrients were examined. A positive association was observed between risk of renal cell carcinoma and total energy intake (odds ratio, OR, for highest quartile compared to lowest: 1.7 (95% confidence interval, CI, 1.0-3.0) for men, and 3.5 (95% CI 1.6-6.5) for women), fat intake (OR for highest quartile compared to lowest: 1.9 (95% CI 1.1-3.5) for men, and 3.3 (95% CI 1.6-6.9) for women). For women, an effect was also seen for intake of carbohydrates (OR for highest quartile compared to lowest: 3.2 (95% CI 1.5-6.8), while no protective effect was seen for vegetables or fruit. Dairy products may be associated with risk of renal cell cancer (OR for women using thickly spread butter compared to thinly spread: 11.4 (95% CI 2.8-45), OR for women who drank more than one glass of milk with 3.5% fat content compared to never drink milk: 3.7 (95% CI 1.2-11). As expected, total energy intake, intake of fat, protein and carbohydrates were closely correlated making it difficult to identify one of the energy sources as more closely associated with risk of renal cell cancer than the other. Several energy sources have been identified as possible risk factors for renal cell carcinoma. It is possible that a high energy intake as such rather than the individual sources are responsible for the increased risk. Furthermore, dairy fats may be associated with renal cell carcinoma risk. The observed associations appeared stronger in women, and did not explain the association with obesity and low socio-economic status previously found in Denmark.