PURPOSE: To evaluate the changes of cerebral blood flow velocity according to the time, before and after surfactant administration in hyaline membrane disease using Doppler ultrasonography. MATERIALS AND METHODS: The patients were 15 premature babies who were clinically and radiologically diagnosed HMD. The ratio of male : female was 11:4, the mean gestational age was 30.1 +/- 2.5 wks, mean body weight was 1.4 +/- 0.6 Kg, mean Apgar score at 5min was 6.28, and type of delivery was C-section : vaginal delivery 9:6. Before and after, 10min, 30min, 1hr, 6hr, 12hr, 1day, 3day, 5day and 7days after surfactant administration, peak systolic and end-diastolic cerebral blood flow velocity (PSFV, EDFV) and resistive index (RI) were estimated by Doppler ultrasonography measuring MCA flow velocity using temporal window. The averages of all data according to the time were obtained and was analyzed statistical significance. For the evaluation of the clinical status, systemic BP, FiO2, pH, and respiratory rate were also checked according to the same time. RESULTS: The clinical status of FiO2, metabolic acidosis, and tachypnea was significantly improved after surfactant administration. There was no significant change of cerebral blood flow velocity (PSFV, EDFV) after the surfac-tant administration. The change of RI was not statistically significant. The changes of the systemic BP had no significant changes. CONCLUSION: In spite of clinical improvement, there were no significant increases of cerebral blood flow velocity and changes of RI after surfactant administration in hyaline membrane disease.