A cohort of 148 patients with papillary Ta-T1 transitional cell carcinomas (TCCs) was followed up for over 10 years and flow cytometric (DNA ploidy, S phase fraction) and morphometric variables (5 nuclear factors, volume corrected mitotic index) were related to prognosis during this period. Recurrence-free survival was significantly related to DNA ploidy, S phase fraction and M/V index. Progression in T-category was predicted by M/V index, S phase fraction, DNA ploidy and WHO grade. The same variables predicted progression in N- and M-categories. In a multivariate analysis only M/V index and S phase fraction were independent predictors of progression. Univariate analysis showed that M/V index, SPF, DNA ploidy and WHO grade predicted survival. In a multivariate survival analysis only M/V index and SPF were independent predictors. The results showed that proliferation indices had independent prognostic value in papillary Ta-T1 TCCs and the grading of these tumours could be based on the proliferation indices. Papillary Ta-T1 tumours with a M/V index value < or = 10/mm2 or SPF < or = 10% had a favourable prognosis whereas tumours with M/V index > 10/mm2 or SPF > 10% had a high malignant potential.