Doppler ultrasonography (US) is a useful, non-invasive method of monitoring renal allograft dysfunction. Thirty-eight living donor transplant recipients had 90 Doppler and real time US studies during the postoperative period. Fifty of these were performed in 18 patients with a normally functioning allograft and 40 studies in 20 patients with renal dysfunction. The resistive indices (RI) measured at the arcuate arteries were 0.56 to 0.7 in those with normal renal function and ranged from 0.70 to 0.88 in allografts with dysfunction. The waveform pattern which was classified into 6 types revealed that types 2,4 and 6 were seen during renal dysfunction; type 1 was not diagnostic of normal, whereas type 3 excluded an abnormality.