OBJECTIVE To design a proper follow-up for cystectomy and ileal conduit urinary diversion for primary bladder transitional carcinoma, we compared the radiographic characteristics of recurrent malignant upper tract lesions with those of benign ureteroileal anastomosis strictures. METHODS Over a 20-year period, we followed 61 patients who underwent cystectomy and ileal conduit diversion at our hospitals for a minimum period of 3 years. Excretory urography was performed routinely at 1, 3, 6 and 12 months after cystectomy and once yearly thereafter. RESULTS Five patients (8.2%) developed malignant ureteral obstruction (4 had metachronous upper tract tumors, and 1 patient had retroperitoneal lymph node metastasis which compressed the ureter). Eleven patients (18.0%) developed benign ureteroileal anastomotic stricture. The interval between cystectomy and initial detection of the malignant and benign upper tract lesion ranged between 34 and 118 months (mean 69 months) and between 1 and 20 months (mean 5.1 months), respectively. In all patients with malignant upper tract obstruction, a complete loss of renal function occurred within 10 months after the detection. Conversely, a progressive renal dysfunction was observed in patients with benign ureteroileal anastomotic stricture. All patients were asymptomatic before the detection of lesions on excretory pyelography. CONCLUSIONS Our results suggest that cancer recurrence can occur even 10 years after cystectomy, typically progressing very rapidly within 1 year. A benign ureteroileal anastomotic stricture, on the other hand, tends to occur within 2 years but advances slowly. Consequently, a proper follow-up necessitates annual excretory urography and/or renal ultrasonography in all patients with ileal conduit urinary diversion after cystectomy.