We reviewed 82 patients with 83 upper urinary tract tumors and investigated those who had associated bladder tumors. Of these patients, 7 (9%) had previous bladder tumors, 14 (17%) had concurrent bladder tumors, and 18 (22%) subsequently developed bladder tumors. As 1 patient subsequently developed a bladder and a upper urinary tract tumor at different times, 38 patients (46%) had associated bladder tumors. The time interval between the occurrence of a previous bladder tumor and the subsequent upper urinary tract tumor was 11 to 144 months (mean: 41 months), while that between an upper urinary tract tumor and the subsequent bladder tumor was 3-31 months (mean: 12 months). Most of the previous bladder tumors were papillary, multiple, and noninvasive (pT1 or less). Multiple upper urinary tract tumors were associated with a high incidence of concurrent bladder tumors, while high-grade (G2, G3) or invasive (pT2 or more) upper urinary tract tumors were associated with a high incidence of concurrent and subsequent bladder tumors. Patients with concurrent bladder tumors had a worse prognosis than those with previous or subsequent bladder tumors due to the increased incidence of high-stage tumors at either the upper tract or bladder site. Our findings suggest that tumor cell implantation is a possible mechanism for the recurrence of bladder tumors and upper urinary tract tumors.