SummaryFour hundred patients were studied with 485 examinations by colonofiberscopy. It was found that any type of colonofiberscope would pass the upper part of the sigmoid colon in almost every patient except those with advanced carcinomas. In patients studied for the purpose of examining the cecum, a success rate of more than 40 per cent was obtained. This procedure is very useful for preoperative diagnosis, cauterysnare resection, and careful long‐term follow‐up studies. It is also advisable for the determination of medical therapy for inflammatory changes, for the determination of surgical procedures for neoplasms, and to help decrease the number of unnecessary laparotomies. Specifications for these colonofiberscopes, examination technics, and some points of improvement are presented. A cooperative understanding from the radiology department which provides fluoroscopic assistance is necessary to ensure safety during the procedure: fluoroscopy permits observation of the position of the fiberscope, and facilitates its insertion, withdrawal, and rotation.