Recently, transcranial Doppler sonography has been introduced into clinical practice for noninvasive investigation of the large intracranial arteries. To determine its accuracy for detection of stenosing or occluding lesions, 133 consecutive patients were studied by both transcranial Doppler sonography and selective cerebral arteriography. Statistical analysis of findings was done separately for various arterial segments. High values for sensitivity and specificity were found for detecting obstruction of the carotid siphon and main stem of the middle cerebral artery. Diagnostic reliability of transcranial Doppler sonography was also confirmed by the calculation of a chance-corrected measure of agreement (kappa), which was close to + 1 in all subanalyses. Transcranial Doppler sonography seems to be a valuable tool for noninvasive detection of intracranial lesions of the middle cerebral artery and carotid siphon.