Between January 1973 and January 1990 we carried out 1,038 kidney transplantations using a transvesical end-to-side implantation of the ureter in the bladder without an antireflux mechanism. Moreover, 30 transplantations were done in 26 patients with a urinary diversion. We examined the urological complications in these 1,068 consecutive transplants. Urinary leakage and obstruction were the two main urological posttransplant complications. Severe leakage occurred in 21 patients (2.0%), and was treated by open surgery; 2 patients had a urinary diversion. The treatment of choice is a pyeloureterostomy (anastomosis between the transplant renal pelvis and the native ureter). There were 35 patients (3.3%) with severe ureteral obstruction of whom 5 had a urinary diversion. In 30 patients open surgical treatment of the obstruction was necessary and in 7 patients a percutaneous endourologic treatment was done (dilatation of a confined ureteral stricture in 6 patients and percutaneous stone treatment in 1). The postoperative mortality in the patients treated for leakage or obstruction was low: 4 patients (7%) died, 3 of septicemia due to leakage and 1 of pulmonary embolism after repair of the obstruction. The results of surgical treatment were good. The graft survival after 2 years in the group of urologically complicated transplants was 68% for the patients with leakage and 80% for those with obstruction. The 2-year graft survival in the patients without complications was 67% and 71% for the patients with a urinary diversion. We conclude from these results that urological complications after renal transplantation can be treated successfully by surgical (or percutaneous) correction.