BACKGROUND Contralateral, metachronous upper urinary tract (UUT) tumors after primary transitional cell carcinoma (TCC) of the UUT are reported rarely, and to the authors' knowledge the risk factors have not been determined to date. In addition, few reports have described the characteristics of recurrent bladder tumors and contralateral UUT tumors and any relation between theses tumor types. METHODS Statistical analysis of data from 223 patients with documented primary UUT-TCC was undertaken. After excluding bilateral involvement and distant metastases, 12 variables were analyzed by multivariate analysis in 189 patients to determine the risk factors for recurrent urothelial tumors. RESULTS The incidence rates of recurrent bladder tumors and contralateral UUT tumors were 31.2% and 5.8%, respectively. Multiplicity was determined as a risk factor for recurrent bladder tumors. Renal insufficiency, uremia, and concurrent bladder tumors significantly predisposed patients to develop contralateral UUT tumors after primary UUT-TCC. The time intervals and stage distributions differed significantly between recurrent bladder tumors and contralateral UTT tumors. Patients who had recurrent bladder tumors had earlier stage tumors and had a shorter time to recur compared with patients who had contralateral, metachronous UUT tumors. CONCLUSIONS For patients with primary UUT-TCC, regular follow-up by cystoscopy is necessary to detect recurrent bladder tumors. Intravenous urography or retrograde pyelography should be performed for patients who have a high risk of developing contralateral UUT tumors.