&NA;In 375 patients who had curative resection for cancer of the rectum below the peritoneal reflection, prognosis was evaluated according to four currently used staging systems,i.e., Dukes' system, the modified TNM system described by the American Joint Committee for Cancer Staging, The Australian Clinicopathological Staging System, and The Astler‐Coller Staging System. Dukes' Staging System, which originally was described for use in rectal cancer, gives as good a prognostic separation as any of the other staging systems, some of which include serosal involvement as a staging criteria, which cannot be used for cancer of the extraperitoneal part of the rectum. It is furthermore demonstrated that an important prognostic separation can be obtained by dividing the B group of Dukes' Staging System into tumors that reach the surface of the muscularis propria and those with demonstrable invasion of extrarectal structures, the latter having as bad a prognosis as Dukes' C tumors.