&NA;A randomized, controlled study on occult blood in stool was conducted in 48,000 asymptomatic participants, ages 50 to 80 years. Those with positive hemoccult test results underwent a complete colonic workup including colonoscopy and, in some cases, an air‐contrast barium‐enema examination when total colonoscopy could not be accomplished. From April 1976 to December 1980, 113 patients (62 men and 51 women), with an average age of 66 years, were found to have invasive carcinomas of the large bowel: right colon−25 per cent, transverse colon (included both flexures)−9 per cent, descending colon−10 per cent, sigmoid and rectosigmoid−42 per cent, rectum−12 per cent, anal canal−2 per cent. The stages of the cancers were: Dukes' A−57 per cent, Dukes' B−21 per cent, Dukes' C−19 per cent, Dukes' D−3 per cent. The findings suggest that a complete colonic workup is required for the detection and diagnosis of large‐bowel cancers in asymptomatic patients.