Objectives : The purpose of this study was to compare cerebral biood flow between hypertensives and normotensives using transcranial doppler ultrasonography (TCD). Methods : I investigated cerebral blood flow of 72 hypertensives and 127 normotensives. To evaluate the cerebral blood flow, I measured the systolic peak velocity(Vs) and mean How velocity (Vm) of the middle cerebral artery(MCA), anterior cerebral artery(ACA), posterior cerebral artery(PCA), basilar artery(BA), and internal carotid artery(ICA) in the two groups using TCD. Result : 1. There was a decrease in the Vs and Vm of all examined vessels of hypertensives in comparison with normotensives. There was a significant difference in the Vs of ACA and Vm of ACA, PCA, ICA. 2. In males, there was a decrease in the Vs of ACA, PCA, ICA and Vm of MCA, ACA, PCA, ICA of hypertensives in comparison with normotensives. However, there was no significant difference in the Vs or Vm of all examined vessels. 3. In females, there was a decrease in the Vs and Vm of all examined vessels of hypertensives in comparison with normotensives. There was a significant difference in the Vs of MCA, ACA and BA and Vm of ACA, PCA and BA. 4. In 30-49 year-olds, there was a decrease in the Vs and Vm of all examined vessels of hypertensives in comparison with normotensives. There was a significant difference in the Vs of ACA and Vm of ACA. 5. In 50-69 year-olds, there was a decrease in the Vs of ACA, PCA, BA, ICA and Vm of all examined vessels of hypertensives in comparison with normotensives. However, there was no significant difference in the Vs or Vm of all examined vessels. 6. In 70-89 vests old. there was a decrease in the Vs. Vm of PCA, BA, ICA of hypertensives in comparison with normotensives. But, there was no significant difference in the Vs, Vm of all examined vessels. Conclusions : There was a significant difference in the cerebral blood now velocity between hypertensives and normotcnsives. These results suggest that blood pressure has influence on cerebral blood flow.