We used the flexible fiberoptic sigmoidoscope (FFS) on 656 subjects who were receiving their yearly physical examinations. Neoplastic disease was disclosed by the FFS in 138 subjects (21%), including 26 adenocarcinomas, 19 of which were out of reach of a rigid sigmoidoscope. Nineteen of the subjects whose adenocarcinomas were found by the FFS had barium enemas, which detected the carcinomas in only 11. Routine FFS in asymptomatic persons is helpful in detecting both premalignant and malignant lesions, it should be seriously considered as a part of regular preventive physical examinations.