In a period of two years, 202 kidneys were transplanted in 162 patients at the Downstate Medical Center. One hundred twenty-nine patients had primary transplantations, twenty-nine second transplantations, and five third transplantations. Urologic complications occurred in twenty-four of the patients (12 per cent). There were eight complications involving the urinary bladder and fifteen ureteric complications. In twenty-one patients the complications appeared within six weeks after surgery. Surgical correction immediately upon diagnosis of the urinary complications resulted in a high degree of early restoration of the urinary tract continuity and preservation of renal function. Leakage from the bladder was frequently associated with previous surgery. In five of eight patients, bladder leakage occurred after the second or third transplantation. Complications of the urinary bladder in general had a significantly favorable prognosis as compared with ureteric complications. Although all the patients with bladder complications fully recovered and maintained good renal function, four patients with ureteric complications either died or lost the graft.