Flow cytometric DNA histograms of colorectal carcinomas from 264 patients were evaluated for the association of tumor site, Dukes' stage, tumor grade, and preoperative carcinoembryonic level with patient survival. The DNA nondiploid carcinomas were significantly more common from the left (descending and sigmoid) colon and the rectum. A poorer prognosis was found for patients with DNA nondiploid cancers than for patients with DNA diploid cancers. This was particularly true for patients with Dukes' stages B2 and C tumors with a small number (one to three) of lymph nodes with metastatic deposits. The DNA nondiploid cancers also had a relatively poorer prognosis in patients with unresectable disease. In a Cox multivariate analysis model, the DNA pattern was an independent prognostic variable for this group of 264 patients with resected colorectal carcinoma.