In 80 patients with primary superficial bladder carcinoma Tumor Nodes Metastasis (TNM classification: stages Ta and T1) with adequate follow-up of at least four years, the value of selective nuclear morphometry and DNA flow cytometry on paraffin-embedded material in addition to classic prognosticators was assessed. Only the quantitative techniques appeared to be valuable predictors of new tumor occurrence. The recurrence rate in patients with large nuclei (mean nuclear area greater than 95 micron 2; n = 29) and in aneuploid cases (n = 30) was significantly higher (Wilcoxon: P = 0.05 and P = 0.0001) than in those with small nuclei (mean nuclear area less than = 95 micron 2; n = 51) and diploid cases (n = 50). The prevalence of large nuclei and aneuploidy also appeared useful to predict progressive recurrence, i.e., grade 3 or/and muscle invasive carcinoma (TNM classification: stages T2-T4) (chi-square: P less than 0.0001). Clinical follow-up showed that only 62.1% of the cases with large nuclei remained free of progressive recurrence, compared with 92.2% of those with small nuclei (Mantel-Cox: P less than 0.0001). For the aneuploid and diploid cases, these figures came to 53.3% and 98% (Mantel-Cox: P less than 0.0001). By multivariate analysis DNA ploidy was selected as the best discriminator. None of the classic prognosticators, including histologic grade, had additional prognostic value. Also, morphometry did not add to the prognosis prediction, which can be explained by the considerable overlapping between the prevalence of large nuclei and aneuploidy (24 of 29 and 30 cases, respectively). These findings practically suggest that patients presenting with superficial carcinoma with large nuclei (mean nuclear area greater than 95 microns 2) or aneuploid DNA values should be treated more aggressively.