Flow cytometry DNA analysis of fragments of fresh or paraffin-embedded tumor was performed in order to investigate its prognostic value in renal cell carcinoma. As aneuploidy is a frequent cytogenetic finding of these cancers, it is not surprising that the literature reports a high incidence of anomalies of DNA content, affecting 2/3 of cases studied. DNA aneuploidy is more frequent in advanced stages, high grades and spindle-cell carcinomas. Its prognostic value in terms of the survival of nephrectomized patients has been demonstrated by unifactorial studies. Several studies using Cox's model have demonstrated its independence of stage and grade, but they are too limited for DNA ploidy to be considered to be an element of the therapeutic decision. In contrast with other sites, the prognostic influence of the proliferation evaluated by S% does not appear to be as important as DNA ploidy. Prospective studies comparing these results should take into account the tumor heterogeneity observed in this type of cancer by analysing, for example, several fragments of the same tumor.