A representative sample of the Belgian population, aged 25-74 years, was interviewed between 1980 and 1985. Dietary habits were assessed using a 24 h food record method. Age-, sex- and district-specific energy-adjusted averages of macronutrient intakes were compared with mortality rates from 1988-90, with special emphasis on the association between fat intake and cancer mortality. Univariate analyses were followed by multiple linear regression analyses, controlling for possible confounders such as fibre intake, smoking and educational level. In multivariate analyses, significant positive associations were found between all-causes mortality and saturated fat intake in men, and between all-causes mortality and the ratio of n-3 to n-6 fatty acids in men; colorectal cancer mortality was associated with polyunsaturated fat intake and with the ratio of unsaturated to saturated fat in men. Significant negative associations were found between all-causes mortality and polyunsaturated fat intake in men, and between all-causes mortality and the ratio of unsaturated to saturated fat in men; colorectal cancer mortality was associated with saturated fat intake in men. In women, only breast cancer mortality was associated with saturated and monounsaturated fat intake. Prostate cancer mortality was not related to any of the studied dietary fat components. For total cancer mortality, only weak non-significant associations with fat intake were found.