SummaryAn autopsy series of 320 patients who had carcinoma of the rectum or sigmoid flexure has been reviewed and a pattern of metastasis plotted with reference to the duration of survival after operation. It is noteworthy that in many of these patients the tumor remained localized for long periods of time.Regional lymph‐node metastasis did not significantly increase after the immediate postoperative period.Hematogenous metastatic spread rapidly increased during the early months after operation. Various factors which may play a part in hematogenous spread have been discussed and therapeutic implications suggested. Some of the clinical implications resulting from this autopsy study have been reviewed.