The control of colorectal cancer has become increasingly important because of its high incidence in the United States of more than 115,000 cases annually. Although 50% of neoplastic lesions of the colon arise in the distal 25 cm of the bowel, endoscopic examination of this area has not been generally accepted. Recent studies with flexible sigmoidoscopes as substitutes for the rigid proctosigmoidoscope, primarily by endoscopists, have shown an increased yield of neoplastic lesions, with excellent patient acceptance. This study reports the development of an initial trial in 200 patients with a 30-cm flexible sigmoidoscope designed mainly for the nonendoscopist general physician for routine office use as a substitute for the rigid proctosigmoidoscope. The instrument provided an excellent examination in minimum time and with good patient and physician acceptance. Widespread application of such instruments by generalists in routine office practice could have a significant impact on the control of colorectal cancer.