&NA;The etiology of cancer of the large bowel is in large part environmental. Both epidemiologic and experimental studies suggest that the environmental factor is dietary, specifically associated with a diet high in fat and low in fiber. Prevention is possible by altering these dietary factors, but the degree of change needed to accomplish it would be too drastic to be acceptable. However, the inclusion of certain additives in a diet only slightly modified with respect to the fat‐fiber content may circumvent this problem. We have evidence that the addition of small amounts of representatives of three classes of cancer inhibitors (retinoids, plant steroids, and selenite) reduces intestinal cancer formation in rats by 50 per cent. This suggests that a diet with modest changes in the fat‐fiber content plus the addition of certain inhibitors may be effective in reducing the incidence of cancer of the large bowel.