['To better define the predictors of bladder tumour development in patients operated for upper urinary tract urothelial cancer (UT-UC).', 'Surgical specimens from 191 consecutive patients with no history of bladder cancer and operated for UT-UC were chosen for analysis. Bladder tumour development was assessed in relation to UT-UC location, tumour multiplicity, stage and grade, margin status, mode of operation, age and gender.', 'Overall, 51 of 191 (27%) patients developed subsequent bladder tumours, including 25 of 123 (20%) with pelvic, 19 of 47 (40%) with ureteric and seven of 21 (33%) with multifocal tumours (P = 0.04 for all subgroups; P = 0.01 for pelvic vs ureteric). There was no influence of the other variables. The median (mean, range) time to recurrence was 12 (18, 3-64) months. In a multivariate analysis, ureteric tumour location was an independent predictor (P = 0.02; risk ratio, RR, 2.0, 95% confidence interval, CI, 1.1-3.7). After excluding 68 patients with systemic disease progression, bladder tumour development was noted in 39 of 123 (32%), including 18 of 76 (24%) with pelvic, 16 of 34 (47%) with ureteric and five of 13 with multifocal tumours (P = 0.06 for all subgroups; P = 0.02 for pelvic vs ureteric). In a multivariate analysis, ureteric location (P = 0.03; RR 2.1, 95% CI 1.1-4.2) and high tumour grade (P = 0.04; RR 2.2, 95% CI 1.03-4.7) were independent predictors of subsequent bladder tumour development.'] Is bladder tumour development after urothelial carcinoma of the upper urinary tract related to primary tumour location?