Ureteral obstruction with impaired urine flow is the most common urological complication following renal transplantation. From December 1976 to December 1997, 869 kidney grafts were performed by our kidney transplantation group, 96 from living related donors and 773 from cadaver donors (736 first grafts and 37 regrafts). A stricture of the ureter (SU) was observed in 27 cases with a follow-up ranging from 18 months to 18 years after the graft and 11 months to 11 years after the treatment of the SU. In six patients, SU was immediately apparent and limited to the anastomosis: they were obviously technical flaws. In all the other patients, there was a free interval ranging from 2 months to 11 years after surgery; the SU usually involved the entire ureter, suggesting multiple etiologies. Repeated urinary infections could be a cause but immunological problems might be more determinant. In our series, acute rejection was more common than chronic so that the correction of SU was followed in many cases by a good and long lasting result (up to 11 years). In our experience, SU was not a dangerous complication even in patients in whom for different reasons (mainly refusal of treatment) the therapy was delayed - even if anuria occurred, no case of graft loss or serious damage were observed. At the beginning of our experience, the diagnosis of SU was based on urography, and therapy has always been re-operation. For 15 years, the diagnosis of SU has been based on routine echographic surveillance, which was intensified after each rejection, and the first treatment of SU in the last 8 years was re-operation in early technical SU and interventional radiology (balloon dilatation with or without temporary stent) in other cases. When it failed or in case of recurrence, surgical correction was performed utilizing the native ipsilateral or contralateral ureter for a uretero-ureterostomy.