The present paper reports the results obtained in 54 patients who underwent a non invasive cerebral vascular examination by doppler technique, followed by a cerebral angiography: a total of 86 carotid arteries were compared. An overall accuracy between arteriographic and ultrasonographic results was found in 69 arteries whereas in 15 arteries there was a discordance; and in only 3 cases ultrasonographic findings resulted false negative. The Authors have also considered the emodinamic and anatomo pathological results obtained in 23 carotid arteries operated on, in order to evaluate ophthalmic test accuracy and noninvasive evaluation of Willis's circle. The Authors have reached the conclusion that doppler technique appears to be inadequate in case of turbulent flow due to arterial dilatation or to non significant stenosis. In addition they have noticed a better reliability of emodinamic findings and a poor accuracy of the ophthalmic test.