To search for reliable parameters that reflect the biological potential of bladder cancer, the argyrophilic nucleolar organizer region (AgNOR), nuclear DNA content and mean nuclear area (MNA) were studied in paraffin-embedded materials of 75 primary transitional cell carcinomas (TCCs) using a quantitative image analyzer, and were also compared with histological findings and prognosis. The AgNOR parameters studied were the mean AgNOR count (C-AgNOR) and the percentage of cells exhibiting more than 4 AgNOR dots within nuclei (P-AgNOR), whereas the DNA parameters were the 2c deviation index (2cDI) and 5c exceeding rate (5cER). These 5 parameters significantly correlated with the histological grade (p < 0.0001, respectively). Similarly, these 5 parameters correlated with the histological stage, but the correlation was higher in 2cDI and 5cER (p < 0.0001, respectively) in comparison with the AgNOR parameters and MNA. Using univariate analysis, the prognostic relevance was noted in all but P-AgNOR. The 5cER value could discriminate histological grade-II tumors in relation to prognosis, whereas the remaining parameters could not. In addition, the significant difference between noninvasive and invasive tumors was noted in 2cDI and 5cER (p < 0.05, respectively), but not in C-AgNOR, P-AgNOR and MNA. These results suggest that (i) 2cDI and 5cER exhibit superiority over the AgNOR parameters and MNA in predicting survival, and (ii) in histological grade-II tumors, evaluation of the 5cER value is most important when predicting survival as well as judging the necessity for further aggressive treatment in patients with TCCs of the bladder.