The aim of this study was to evaluate the relationship between DNA ploidy, proliferative activity and other prognostic factors and the survival of patients with colorectal cancer. 45 patients were prospectively investigated for 6 years. Fresh multiple samples for flow cytometric analysis of DNA content were collected during surgical resection of primary tumor. A 42% frequency of aneuploidy was observed with a median DNA index value of 1.54. The proliferative activity (%S+G2M cells) was higher in the aneuploid cell sub-population (28.6%) compared to the diploid counterpart (22.7%)(p = 0.05). No significant relationship between DNA ploidy and tumor site, Dukes' stage, histological type, grading age or sex was observed. No correlation between DNA ploidy and survival was demonstrated, including in the analysis of patient subsets according to stage. No additive prognostic information was obtained from a breakdown analysis as a function of DI values, percentages of aneuploid cells and proliferative activity. This study suggests that flow cytometric content analysis lacks prognostic value in colorectal carcinoma.