We reviewed our experience with 12 renal transplant patients who had urine leaks to compare the accuracies of sonography and nuclear renography with that of antegrade pyelography in establishing the diagnosis. The leak was proved by surgery in 11 of the 12 cases. We also determined the role of diverting percutaneous nephrostomy drainage in the treatment of such leaks. The diagnosis was established by sonography in eight (67%) of the 12 patients. Nuclear renography, performed in nine patients, showed decreased renal function but showed the leak in only three (33%) of the nine cases. Antegrade pyelography, performed in all 12 patients, showed leakage in 10 (83%). In the other two patients, follow-up nephrostograms done within 24 hr showed leaks near the ureterovesical anastomotic site. Seven of 11 patients who were managed with a combination of percutaneous nephrostomy drainage and surgical reconstruction were treated successfully (i.e., a functioning graft was retained); however, only one patient was managed successfully by percutaneous methods alone. Antegrade pyelography is more accurate than sonography and nuclear renography in the detection of urine leakage after renal transplantation. However, percutaneous nephrostomy drainage appears useful only as an adjunct to surgery for treatment of this complication.