In a series of 107 patients treated over an 11-year period for upper urinary tract tumours (UTT), 30 had a synchronous or metachronous associated bladder tumour. The bladder tumour preceded the UTT in 10.3% of cases, the bladder tumour was synchronous in 6.5% of cases and the bladder tumour occurred after the UTT in 15% of cases, the incidence of UTT after cystectomy over this 11-year period was 3.3%. The median time to recurrence of the UTT after bladder tumour was 17 months. The median time to recurrence of the bladder tumour after the UTT was 12 months. The risk of bladder recurrence after treatment of the upper tract tumour was studied in relation to site, type of treatment, multifocal nature, stage and grade of the UTT and the presence of a previous or synchronous associated bladder tumour. None of these parameters constituted a predictive factor of bladder recurrence after treatment of an upper tract tumour. Comparison of survival between the UTT + bladder tumour group and the UTT alone group did not reveal any significant difference (p = 0.10). The theory of cellular implantation facilitated by vesicorenal reflux and the multifocal theory are complementary explanations of the multifocal and recurrent nature of urothelial tumours.