Over a 5-year period, 185 patients with primary colorectal carcinoma were studied by colonoscopy for synchronous neoplasms. Twenty-eight patients had incomplete examinations due to obstructing tumors, and 157 had total colonoscopy. Sixty patients (35.9%) had synchronous neoplasms, of which 43 (25.7%) were adenomatous polyps, 5 (3%) were villous polyps, and 12 (7.2%) were carcinomas. The planned surgical procedure was altered on 7 of 12 synchronous cancers (58.3%), 10 of 38 adenomatous polyps, and 17 of 157 (10.8%) patients who underwent total colonoscopy. Preoperative colonoscopy is deemed essential for the optimal management of the patient with colorectal carcinoma.