Among 190 patients operated on for transitional cell cancer of the renal pelvis and/or ureter from 1976 to 1990, 95 had their tumor studied by flow cytometry. Of these, the prognostic significance of the DNA ploidy pattern with respect to the standard pathologic features was assessed in a retrospective analysis, where survival information were updated to October 1991 and the mean follow-up of patients exceeded 5.5 years (longest follow-up: 15.5 years). Five and ten-year survival probabilities for the whole group were, respectively, 65.5 and 51%. Patients with a diploid tumor had significantly better survival rates than patients with tetraploid/aneuploid cancer (p less than 0.00001). The impact of the DNA ploidy on survival was confirmed by a multivariate analysis of prognostic factors, where only tumor grade (p less than 0.0001), tumor stage (p less than 0.0001), number of neoplastic foci (p = 0.022) and nuclear DNA pattern (p less than 0.068) had a significant influence on survival. In the group of patients with low-stage (pTa-pT1) and low-grade (G1-G2) transitional cell cancer of the upper urinary tract, the DNA analysis was unable to identify any subset of patients at higher risk for disease progression.