In a case-control study of cholecystectomy and carcinoma of the colon conducted in a residential retirement community near Los Angeles, California, no significant association was found, either for all colonic cancer (relative risk = 1.2) or by subsite (relative risk = 0.8 for right-sided colonic cancer and 1.3 for other colonic cancer). Because of this negative finding and the inconsistency of other epidemiologic studies, certain aspects of the descriptive epidemiology of colonic cancer in Los Angeles were examined to see if they were consistent with a major etiologic role for cholecystectomy. The distribution of right-sided colonic cancer by sex and race contrasted sharply with that expected, based on the known distribution of cholecystectomies in the population. Cholecystectomy is unlikely to be an important factor in the etiology of right-sided colonic cancer.