Prospective evaluation of lower limb arterial blood flow velocity and vascular complications of percutaneoustransfemoral arterial catherterization was carried out in 26 children at S.N.U.H. Children's Hospital from Dec.1985 to May 1986. Common femoral and popliteal arterial velocity signals of both limbs were monitored and comparedby doppler duplex sonography(Diasonics DRF-400) immediately after angiography and at 24-48 hours later. In mostcases, the average velocity of proximal femoral artery and popliteal artery of puncture site was slower than thatof the other limb vessels. In complication group of thromboembolism(19%), the catheterization time was longer, thecatheter size was larger, the velocity discrepancy of both limb arteries was larger, the doppler velocity profilewas more irregular, and the diurnal change of arterial velocity discrepancy was slower than in normal controlgroup. It is recommended that the catheterization time is less than 30 minutes and the catheter diameter is lessthan two-fifths of the femoral arterial diameter. Systemic heparinization within 24 hours is required if thecatheterization time is longer of blood flow disturbance is detected on doppler examination. The doppler duplexsonography is a simple, rapid, and noninvasive technique for assesing lower limb hemodynamic, especially inpatients undergoing transfemoral arterial catherization.