Two hundred twenty-two patients with colon cancer, diagnosed in the past 5 years, were grouped by age into the sixth, seventh, and eighth decades. Examination showed an increased incidence of right-sided colon cancer by decade and a simultaneous fall in the incidence of rectosigmoid lesions. A trend toward a more favorable Dukes' pattern was evident with each rise in decade. We suggest that the shift in site of colon and rectal cancer toward the right is directly related to age and is a feature of the "aging gut."