The cerebral blood flow velocities (CBFV) of infants with perinatal asphyxia and hypoxic ischemic encephalopathy (HIE) in the first 12 hours of their lives have been the chief focus of our concern in this study. Cerebral ischemia which can develop in the earlier hours of HIE, and the detection and diagnosis of this condition with color Doppler ultrasonography (cD-USG) will be put into discussion. Twenty-three full-term newborn infants who had perinatal asphyxia and HIE together with a control group constituting twenty full-term newborn infants who produced no problems, were included in our study, All of the infants underwent cD-USG in the postpartum period of the first 12 hours (mean 8.4 hours). Measurements being based upon peak systolic velocity (PSV), end diastolic velocity (EDV) and Pouecelout's resistive index (RI) in anterior and middle cerebral arteries were conducted. The infants, having been discharged from the unit they were followed up for mean 9.8 months in the outpatient clinic. PSV and EDV counts in the postpartum first 12 hours of 23 infants who were detected to have HIE were found to be significantly lower compared to the control group, whereas RI counts were found to be significantly higher (p < 0.05). The counts obtained from the right and left cerebral arteries of the infants with HIE were found to be corraleted with each others. The neonates in the patient group were observed to have gone through this prognosis: Three of them died, three of them had cerebral palsy, one of them had infantile spasms, and three of them had developmental retardation. When we compared the CBFV of the 10 neonates who had poor prognosis, retrospectively with the other 13 neonates who had good prognosis, PSV and EDV were found to be significantly lower and RI significantly higher (p < 0.05). In the light of the data we have obtained, cD-USCT can be considered to be a highly practical device in evaluating CBVF of the infants with HIE. A skillful detection of the decrease in cerebral blood flow which can develop in the postasphyxial first 12 hours and the prospective treatments being based upon this approach would contribute to the diagnosis, treatment and. prognosis of such cases. - Doppler; neonatal; cerebral blood flow velocities (C) 2002 Tohoku University Medical Press.