Examinations with directional Doppler (DD) with 10 MHz transducer, and pulsed Doppler in combination with two-dimensional sector scanner with 3 MHz transducer (Duplex) were carried out on 100 vessels in 51 patients with transitory ischemic attacks (TIA) and minor stroke within the territory of the internal carotid artery before angiography. The question at issue was to evaluate the accuracy of both methods in discriminating between occlusion and stenosis. A correct diagnosis was made by DD in 92 vessels out of 100 and by Duplex in 98 out of 100. All nine occlusions were correctly diagnosed by Duplex, but only five of them by DD, while the four remaining vessels were considered as stenosis greater than 50%. Out of 15 stenoses greater than 50%, 14 were correctly detected by Duplex and 11 by DD. One patient with tortuous vessel without stenosis was classified as greater than 50% stenosis by Duplex, and one vessel with 1 mm lumen was called occlusion by Duplex and DD. In conclusion, the Duplex scanner offers increased possibility to differ between high-grade stenosis and occlusion of the carotid arteries as compared with earlier non-invasive techniques.