Quantification of argyrophilic nucleolar organizer regions (AgNORs) stained by the silver colloid method in urinary exfoliative cells from 36 benign urological diseases and 33 transitional cell carcinomas (TCC) of the urinary bladder was carried out. Also, AgNORs of these cells were measured by means of the computer-assisted image analysis system. There was a significant correlation between AgNORs numbers of cells from voided or wash-out smears and those from touch smears (p less than 0.01). The mean AgNOR numbers per nucleus showed a stepwise increase from non-infected benign urological diseases (mean +/- SD: 3.33 +/- 0.60) through infected urological diseases (3.88 +/- 0.58), grade 1 of TCC (5.23 +/- 1.39) and grade 2 of TCC (6.34 +/- 0.86), to grade 3 of TCC (8.09 +/- 1.19). The maximum number of AgNORs in each group indicated almost the same results. The estimation of the distribution of the maximum AgNOR number might be of great value for rapid and reliable detection of bladder cancers. Moreover, the computer-assisted image analysis of AgNORs could offer an objective index for the cytological assessment of urinary bladder diseases including TCC.