Flexible fiberoptic gastrointestinal endoscopy has greatly simplified the diagnosis and treatment of colonic volvulus. The management of 39 patients with colonic volvulus treated over 9 years was reviewed. Five per cent were treated with rectal tube decompression alone, 23% were treated with either sigmoidoscopic or colonoscopic reduction, and 26% were treated exclusively with operation. Endoscopic reduction was attempted in nearly half of the patients in preparation for operation. Recurrent volvulus occurred in 57% of patients initially treated with endoscopic reduction alone. Sigmoidoscopic examination did not confirm the diagnosis in 24% of instances in which it was used, although colonoscopy was always diagnostic. The overall mortality rate was 8%, but increased to 25% in patients with gangrene of the colon. Three patients who later proved to have gangrene of the colon had a normal initial sigmoidoscopic examination. Two of these patients died of intra-abdominal sepsis from a perforated colon. In five patients an accurate endoscopic diagnosis of gangrene prompted immediate exploration. None of these patients died. Endoscopy is a safe and effective diagnostic tool for the initial evaluation of patients with suspected colon volvulus. In addition, endoscopy may result in therapeutic decompression and may provide visual assessment of the viability of the bowel mucosa, thus assisting in the timing of appropriate operative treatment.