The histopathologic and clinical findings in 682 patients with carcinoma of the rectum have been analyzed. Invasion of veins and nerves by primary growth was found in 38.9 and 34.9 per cent, respectively. The five-year survival rate for patients with resectable tumors was 49 per cent. The age, Dukes' staging, and presence and/or absence of liver metastases, of venous invasion, and of nerve invasion were found to be of statistically significant importance for the prognosis. Sex was found to be on the borderline of significance and Broders' grading was even less significant. Invasion of veins was found statistically significant more frequently than nerve invasion, but the present investigation revealed the importance of the invasion of veins as well as of nerves. When venous invasion was observed, liver metastases developed over three times as frequently in these patients as when metastases were not demonstrated. In contrast to Dukes' staging. Broders' grading can be applied to tumor biopsies preoperatively. The importance of venous and nerve invasion for the selection of patients for adjuvant therapy after termination of surgical treatment is discussed.