Hypertension in renal transplant recipients is an important risk factor for graft function and cardiovascular morbidity and mortality. The mechanisms of posttransplant hypertension are multifactorial. Rejection, both acute and chronic, recurrent renal disease, graft renal artery stenosis, native kidney disease and drug therapy with steroids and cyclosporin have all been implicated. Where a single cause can be identified, the therapy can be rational and often very successful. For this reason, the diagnosis of graft renal artery stenosis is important, because percutaneous transluminal angioplasty or surgery can lead to the cure of hypertension and improvement of the graft function. Previously a study was performed in our center about post transplantation hypertension in adult patients, The incidence of hypertension in these patients was 61% and 1.64% of them involved by renal artery stenosis. Thus we decided to determine the incidence of renal artery complications in pediatric renal transplantation. We assessed 34 children with renal transplantation with noninvasive Doppler sonography for renovascular complication in labbafi nejad Hospital. The cases with renal artery stenosis by Doppler sonography were assessed by captopril DTPA scan for confirmation. Mean age of patients was 11 years old. 57% of our patients were male. The etiology of our patients was: neurogenic bladder 11 patients, medullary cystic disease 5, glomerulonephritis 10 patients, reflux nephropathy 2 patients, hypodysplasia 6 patients. Most of them was dialyzed before transplantation.Doppler ultrasonography was performed for all patients. The mean time duration after transplantation was 4 years. 25 patients (73%) had normal blood pressure before transplantation. 14 patients had normal blood pressure after transplantation. Thus 20 patients (58%) had high blood pressure after transplantation which of them 12/20 found hypertension after transplantation. Acceleration time, RI, Velocity was measured for renal artery, interlobar arteries in upper, m iddle and lower lobes. Of 34 patients 3 patients had the findings of renal artery stenosis in Doppler sonography. Of these only one patient had the findings of renal artery stenosis in captopril DTPA scan. She had normal blood pressure before transplantation. The delayed graft function and hypertension immediate after transplantation was seen in this patient. The last creatinine (1 year after transplantation) was 1.2 mg/dl.