Chronic inflammatory bowel disease (CIBD) and colorectal adenoma are considered as precancerous conditions and lesions of large bowel carcinoma, respectively. They, therefore, may be used to study the behavior of such different factors as tumor-associated antigens and nuclear DNA content abnormalities in colorectal carcinogenesis. Tissue concentrations of carcinoembryonic antigen (CEA) were significantly higher in those precancerous lesions (CIBD: 61 +/- 11.2 ng/mg, adenoma: 70 +/- 6 ng/mg; mean +/- standard error of the mean) than in normal colonic mucosa (36 +/- 4.7 ng/mg). Colorectal carcinoma had still higher tissue levels (437 +/- 108.2 ng/mg). No correlation between tissue CEA and tumor differentiation could be found, but there was a significant difference between aneuploid (747 +/- 354 ng/mg) and diploid (139 +/- 43 ng/mg) tumors. Using flow cytometry DNA aneuploidy was present in 31.6%, 10.5%, and 51.6% of CIBD, colorectal adenoma, and carcinoma, respectively. These data suggest that the occurrence of aneuploidy is not strongly dependent on a malignant transformation, but it may also be present in premalignant colorectal lesions without cellular dysplasia.