We performed transcranial Doppler ultrasonography of the middle cerebral arteries in 43 patients who underwent cerebral angiography. Twelve patients had normal arteriograms, 18 had internal carotid artery stenosis, and 13 had complete occlusion. Parameters measured included: flow velocity (mean, maximum, and peak systolic), flow acceleration, systolic-to-diastolic ratio, and pulsatility index. Patients with 75% to 100% stenosis had lower average ipsilateral flow acceleration and mean velocity than did normal subjects. Correlation analysis revealed an inverse relationship between degree of stenosis and ipsilateral flow acceleration, as well as ipsilateral mean velocity. These correlations were no longer significant when we excluded normals, however. There was a linear relationship between right and left velocity values for both normal subjects and patients with occlusion but not for patients with stenosis. This technique has potential for the reliable assessment of the hemodynamic effect of carotid stenosis on intracranial circulation.