A multi-centre case-control study on bladder cancer and diet was carried out in 5 regions of Spain. We report results on 432 male cases and 792 matched controls. Usual dietary habits were investigated by means of an interview-based dietary history questionnaire. Bladder-cancer cases were selected from the registers of 12 hospitals located in the study areas. Each case was matched by sex, age and area of residence to 2 controls, one identified in the same hospital and one drawn from population lists. Descriptive analyses indicated that the average dietary pattern was typical of Mediterranean populations: a high P/S ratio, high intake of fish, fruits and vegetables and moderate or low intake of meat and dairy products. Relative risks for specific foods and nutrients were adjusted for tobacco smoking and energy intake. Subjects in the highest quarter of intake of saturated fat had a significantly increased risk of bladder cancer (RR for highest quarter = 2.25; 95% CI = 1.42 to 3.55). Moderate increases in risk for high intake of mono-unsaturated fats and calcium, and a slight decrease for iron were also found, but these disappeared after adjustment for saturated fat. Intake of vitamin E was related to slightly reduced risk (RR for highest quarter = 0.72; 95% CI = 0.48 to 1.09) which was not modified by adjustment for fat. No association was found with intake of retinol or carotene. These results, along with those of previous studies, suggest that saturated fat intake may influence the occurrence of bladder cancer.