One hundred and one consecutive patients complaining of dizziness were assessed by noninvasive carotid-artery testing, including oculoplethysmography, supraorbital directional Doppler and direct carotid flow Doppler. Hemodynamically significant carotid disease was found in 8 of 34 patients with the nonspecific complaint of "lightheadedness," in 4 of 21 patients with syncope, in 3 of 12 patients with vertebrobasilar insufficiency, and in 7 of 27 patients with associated focal cerebral signs or symptoms. None of 7 patients with vertigo alone were affected. In summary, 21 of the 101 patients with dizziness had hemodynamically significant obstruction to flow in the carotid-artery circulation. These findings suggest that in a fairly large proportion of patients complaining of dizziness, the symptoms may be the result of decreased cerebral perfusion due to carotid-artery occlusive disease. In these patients, noninvasive carotid-artery testing appears to be useful in identifying those with significant obstruction to blood flow in the carotid-artery circulation.