Abstract: Objective To explore the changes of cerebral hemodynomics in patients with virus encephalitis(VE). Methods Within the initial 24 h and 21 days after admission, respectively, the patients with acute VE(n=38) suspected to result from viral infections were examined with serial transcranial Doppler ultrasound(TCD) for measurements of the systolic flow velocity(Vs), mean blood velocity(Vm) and the pulsatility index(PI) in the middle, anterior and posterior cerebral arteries(MCA, ACA, PCA) and the basilar artery(BA). Results TCD showed normal findings in 11 and abnormal findings in 27 patients, with a positivity rate of 71%. The Vms were significantly elevated in MCA, ACA, PCA, vertebral artery and BA during the acute phase of VE compared with that of the 30 normal control subjects(P<0.001-0.05). The PIs were significantly increased in MCA, PCA and BA(P<0.001). Conclusion TCD findings indicate the presence of cerebral vasospasm in VE during the acute phase.