To evaluate the clinical application of the ultrasonic Doppler technique, renal arterial blood flow was measured in 7 normal subjects and 3 patients with renal dysfunction. For the purpose of correction of blood flow measured by the Doppler technique, some basic studies were performed. The ratio of peak diastolic to peak systolic velocity (D/S ratio) correlated well with both the creatinine clearance and the CA ratio calculated from the results of Dynamic CT. There was no correlation between the corrected velocity of the arterial blood flow and the creatinine clearance. The D/S ratio obtained by the ultrasonic Doppler technique is thought to be a useful parameter in the evaluation of the renal function. However, the Dynamic CT is thought to be superior in objectiveness to the ultrasonic Doppler technique.