We measured the blood flow velocity of the anterior cerebral artery via anterior fontanelle approach of fifty five preterm neonates with duplex Doppler sonography and analyzed the waveform and calculated pulsatility index were increased with increasing gestational age, birth weight, and age of the neonate, but resistive indices decreased. In sick babies, characteristic resistive index increment were seen in patients with intraventricular hemorrhage, but no statistical difference was seen in patients with respiratory distress syndrome. Our results suggest that duplex Doppler sonography is a use ful noninvasive means of monitoring cerebrohemodynamics in normal pretem neonates and flow change of sick babies.