The investigation deals with Ki-67 immunoreactivity assay in upper urinary tract transitional cell carcinoma (TCC) with respect to grade, stage and survival after radical surgery. In a retrospective study (5yrs) of 37 patients with TCC of the renal pelvis and ureter, who had undergone radical nephroureterectomy and bladder resection, pT1-pT4 lesions and G1-G3 tumors were identified. Ki-67 expression was evaluated by immunohistological staining (1:100; MIB-1; Immunotech. Inc., Westbrook, USA). By using fifteen x600 visual fields, Ki-67 labeling index (number of positive cells per 100 tumor cells) was found (mean +SD--29.7 +/- 9.22). There was a correlation between the index and tumor stage (p < 0.001) and grade (p = 0.002). The Ki-67 values in excess of 27 corresponded to high risk of bladder recurrence (p < 0.001) and short duration of recurrence development (p = 0.067) whereas, for the index of under 22, five-year progression-free survival was more frequent (p < 0.001). Having been tested in that study, discriminative modeling yielded the following parameters: sensitivity and specificity for bladder recurrence was 93% and 79% while for 5-year progression-free survival- 89% and 100%.