Color Doppler sonography indices, such as resistive index (RI) and pulsatility index (PI), can predict arteriolosclerosis of internal renal vessels in kidney transplantation. In the other hand, the blockage of Angiotensin II receptor with angiotensin II receptor antagonists could have antiatherogenic effects. The aim of this study was determining the effect of losartan on Ris of renal allograft. In a randomized, blinded, controlled trail, we compared treatment group by losartan ( 25 mg two times daily) with control group for changing of duplex sonographic measurements in renal allograft recipients ( male = 30, female = 20) from living donor. The patients in the two groups had similar base-line characteristics. 49 patients (losartan group: 24 and control group: 25) completed twelve months follow up. After 12 months, the mean RI and of intrarenal and main artery in the losartan and control groups were (0.71 ±0.06 vs 0.69±0.07, P = 0.4) and (0.74 ±0.07 vs 0.72±0.07, P = 0.3) and for PI (1.3±0.25 vs 1.29±0.28, P = 0.8) and (1.5±0.3 vs 1.4±0.34, P = 0.3) respectively. Losartan have no effect on Doppler sonography indices. However, longer follow up is needed to confirm this issue.