The development of colorectal surgery during the last 35 years was analyzed on the basis of case reports of a University Surgical Department. It was found, that lethality of the procedure was reduced during this period and that the number of tumor resections per year increased. In cases of carcinoma of the rectum extirpation of the rectum was reduced in favour of deep resection of the tumor in the recent time. In addition the analysis showed, that time of hospitalization was definitely reduced. Postoperative results have improved considerably due to improved methods of preparing the intestinal tract for surgery, due to preoperative prophylactic treatment with antibiotics--this reduces the postoperative need of antibiotics rather definitely--but only due in a limited extent to change of suturing techniques. The extent of pre- and postoperative diagnostic and therapeutic procedures increased, which however was justified because results improved quite definitely.