Proctoscopes have long been the conventional device for examining the lower intestine for carcinoma, polyps and other disorders. Their inflexible design has restricted examinations at best up to 20 to 25 cms. A manipulable, flexible fiber optic instrument has been developed which allows up to 55 cms of the lower intestinal tract to be examined without the need of surgery. The development of the fibersigmoidoscope and its use in examining patients in addition to other diagnostic instruments using synthetic fiber optics will be discussed. This work is under development through Health, Education and Welfare with Dr. B. G. Overholt, of the University of Michigan.