Flow cytometric analysis of cellular DNA content was performed on 78 biopsy bladder samples obtained from 61 patients with bladder tumors. All 6 normal tissue samples and 1 benign papilloma exhibited a cytometrically diploid DNA distribution, while 39 of 60 bladder carcinomas exhibited at least one aneuploid cell subpopulation. Furthermore, 13 of 39 aneuploid tumors were characterized by the presence of more than one aneuploid cell subpopulation. The results indicate a significant relationship between cytometric ploidy and morphological classification and stage: the occurrence of subpopulations with abnormal DNA content is associated with the increase in differentiation grade and stage. A significant statistical difference in the survival pattern between the diploid and aneuploid groups was observed. The percent of S cells extracted from DNA content distribution histograms indicates a statistically significant difference (p less than 0.01) between normal tissue (3.7 +/- 1.8), diploid tumor (8.4 +/- 3.9) and aneuploid tumor (14.9 +/- 6.0). Moreover the percent of S-phase cells increases with grade in only the aneuploid subgroup. Our results suggest that cytometric parameters in association with morphological and clinical criteria can contribute to a more accurate characterization of bladder tumors in prognostic terms.