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 abovementioned dietary factors (in the body mass analysis), and browned meat surface had little or no influence on the results.