Transcranial color-coded real-time sonography (TCCS) and cranial computed tomography were applied to patients with middle cerebral artery (MCA) stenosis to evaluate whether these techniques may disclose additional aspects of the pathophysiology of the stenotic lesion. In 15 patients with MCA stenosis identified by transcranial Doppler sonography, the echogenicity of the stenotic segment was estimated subjectively by TCCS. The density of the stenotic segment, prior to being detected by TCCS, was quantified by computed tomography. In 5 of the 15 patients, transcranial imagedirected Doppler sonography identified a hyperechogenic lesion in association with the stenotic vascular segment; computed tomography demonstrated a "dense" artery (Hounsfield units [HU] >120) in the corresponding vascular segment. In 10 patients the echogenicity of the stenotic segment was found to be normal, with a computed tomography density of < 100 HU in the corresponding segment. Hyperechogenic and hyperdense stenotic vascular segments in TCCS and computed tomography, respectively, may indicate an arteriosclerotic vascular lesion with calcium deposits. Normal echogenicity and normal to slightly elevated computed tomographydensity of a stenotic vascular segment may suggest the presence of a thrombotic/ embolic lesion.