Vertebrobasilar intracranial stenoses seem to carry a higher risk of brain stem ischemia than proximal vertebral artery stenoses. Our aim was to assess the value of transcranial Doppler sonography versus angiography in detecting and quantifying these intracranial stenoses. All consecutive patients who underwent transcranial Doppler sonography prior to angiography from 1989 to 1994 and whose sonograms showed a stenosis of greater than 50% of one vertebral artery (21 cases) or of the basilar artery (eight cases) were included in the study. These patients were compared with 60 other consecutive stroke patients studied via transcranial Doppler sonography prior to normal vertebrobasilar angiography The transcranial Doppler sonographic criteria for stenosis were a peak systolic frequency shift greater than 2 KHz. A tight stenosis was identified by this pattern combined with direct and reverse low frequencies of high spectrum energy. The sensitivity of transcranial Doppler sonography using a peak systolic frequency shift in diagnosing stenoses reached 80% and its specificity was 97% if only atheromatous stenoses were considered. The main diagnostic failures concerned bilateral stenoses or contralateral occlusion, tandem lesions, and upper basilar artery stenosis. Transcranial Doppler sonography underestimated the degree of stenosis compared to angiography in 55% of the cases. We conclude that transcranial Doppler sonography is accurate in recognizing a stenosed vessel in the intracranial vertebrobasilar circulation, but if this finding will alter therapy, the examination must be complemented by magnetic resonance angiography.