Diuretic renal scan, a modified method of conventional radionuclide renography by administration of intravenous furosemide was performed in 54 patients with suspected urinary tract obstruction. Two showed normal responses, 41 showed increased washout patterns, and the remainder 15 revealed no changes in response to the furosemide administration. IVP was done in 34 patients. In comparision to the diuretic renal scan, the following results were obtained. 1) Patients with normal results by the scan, showed normal IVP findings also. 2) 10 patients who showed delayed excretory patterns not influenced by the diuretics administration. 9 patients revealed obstructive lesions and hydronephrotic changes, and CPN was diagnosed for the remainder one and the one patient without obstruction was diagnosed as chronic pyelonephritis. 3) 22 patients showed positive results to the diuretics. Among them 10 patients had positive results in IVP. but, were not related to the speed of decrement of the renal activity after the furosemide administration.