Two hundred sixty one patients with adenocarcinoma of the colon and rectum were studied with respect to histopathologic and macroscopic tumor characteristics. Nonmetastatic disease was associated significantly with well-differentiated tumors, tumors with pronounced inflammation, and polypoid adenocarcinomas. There was a higher proportion of poorly-differentiated tumors in the right colon. Inflammatory changes were uncommon in rectal lesions; these tumors were more often polypoid than in other locations. Survival was significantly influenced by tumor differentiation, degree of inflammation, macroscopic appearance, and tumor size. Well-differentiated adenocarcinomas, less than 2 cm in diameter, and well-differentiated polypoid adenocarcinomas, less than 4 cm in diameter, were all found in patients with Dukes' stage A tumors. Such patients may be candidates for local excision if the tumor is located in the distal part of the rectum.