Results from epidemiogical studies have provided clues as to etiological factors involved in the development of large bowel cancer. Overnutrition, especially in terms of dietary fat consumed, appears to be a key etiological variable affecting the rate of colon cancer. Epidemiologists can provide the leads for chemists and bacteriologists to pursue in population groups and for experimentalists to test in laboratory animals. Coordination of and cooperation between many disciplines is necessary in order to contribute to the prevention of this man-made disease.