A population-based case-referent study on diet (total energy, protein, fat, dietary fiber), body mass and colorectal cancer was performed in Stockholm in 1986-1988. The study included 1,081 subjects. The relative risks (RR, with a 95% confidence interval, highest versus lowest quintile) for colon cancer were as follows: total energy (1.7, 1.0-3.0), protein (2.4, 1.5-4.0), total fat (2.2, 1.3-3.6), dietary fiber for men (0.5, 0.2-1.1), dietary fiber for women (1.2, 0.7-2.3) and body mass (2.0, 1.3-3.1). The relative risks for rectal cancer were: total energy (2.4, 1.2-4.7), protein (3.6, 2.0-6.4), total fat (2.5, 1.4-4.6), dietary fiber (0.5, 0.3-0.9), body mass for men (1.7, 0.7-4.0), and body mass for women (1.0, 0.5-1.9). Adjustment for physical activity, body mass (in the diet analysis), the above-mentioned dietary factors (in the body mass analysis), and browned meat surface had little or no influence on the results.