The transcranial Doppler sonographic findings of 40 patients with middle cerebral artery (MCA) territory infarction were compared with those of 40 controls. The results showed that in the group of acute phase patients there was a large reduction of MCA mean flow velocity (Vm) of the infarcted side compared with the normal hemisphere (P < 0.01) and controls (P < 0.05). At the same time the anterior cerebral artery (ACA) Vm rose on both sides (esp. on the infarcted side) in comparison with controls (P < 0.05). The posterior cerebral artery (PCA) Vm did not change significantly (P > 0.05). In the group of chronic phase patients there were changes similar to the group of acute phase patients in MCA Vm and ACA Vm, but not statistically significant. Follow-up TCD examinations were carried out in 8 cases during the acute phase of stroke. We found that the decreased MCA Vm on the infarcted side returned to normal in 4 cases, remained lower in another 2 cases within 4 weeks after onset. The increased MCA Vm on the infarcted side in 2 cases returned to normal within 2 weeks after onset. Various types of TCD findings in patients with MCA occlusion were described and analysed.