For several authors, DNA tumoral cell content represents an important prognostic factor in colorectal cancer. Samples obtained from 65 human colorectal cancers operated on between 1983 and 1986 were studied. Of 52 cases studied by flow cytometry 60 p. 100 were aneuploid tumors. The proliferative index was calculated in slightly over 50 p. 100 of the cases by DNA histogram analysis. During the same period 30 tumoral karyotypes were established by cytogenetic analysis. In 17 cases a comparison was possible between flow cytometry and cytogenetic results. In all cases a significant correlation was seen between the DNA histogram modal value and the mean number of chromosomes counted by cytogenic analysis. In this study, there was no statistical correlation between flow cytometry results and Dukes classification. Because of the short follow-up in our series, no prognostic value may be attributed to the DNA index.