Twelve patients (8 males and 4 females) with toxic dilatation of the colon in acute ulcerative colitis were reviewed, who required surgery between 1962 and 1974 at the Department of Surgery, University Kiel. This complication always occured during a relapsing exacerbation of known colitis. Nine patients died. This high operative mortality (75%) was related to faecel sepsis because of praeoperative perforations, operative disruptions of walled-off perforations and to a delaying conservative approach of more than ten days. These results with the onestage coloproctectomy or colectomy with later excision of the rectum urge an early surgical intervention before perforation took place. The diverting ileostomy and decompression colostomy may additionally lead to a better prognosis.