Nineteen cases of amaurosis fugax (AF) were analyzed in clinical study undertaken to address the problem of its pathogenetic mechanism. This series comprised 10 male and 9 female with an age range of 26-77 years. In 8 cases, AF was the only clinical manifestation, while in the other 11, AF was accompanied by hemispheric TIA. The attack lasted for a few to 15 minutes on most occasions, occurring on the left side in 7 cases and on the right in 12 cases. On the basis of cerebral angiographic findings and findings on transcranial Doppler blood velocity measurements (TCD), these cases were classified into 4 types of different etiology, i.e. (Group A) micro-embolus via internal carotid artery origin--7 cases (5 with stenosis at the level of siphon, 2 with stenosis of the ophthalmic artery); on TCD the direction of blood flow in ophthalmic artery was normal (forward flow) in 5 cases and antiplatelet therapy proved effective in 4 cases, (Group B) micro-embolus derived via the external carotid artery--5 cases (3 with complete occlusion of internal carotid artery at its origin, 2 with severe stenosis there of); TCD showed blood flow in the ophthalmic artery to be in a direction opposite to the normal (away flow) in 3 cases and 3 cases responded favorably to antiplatelet therapy, (Group C) cerebral hemodynamic crisis--3 cases (severe cardiac hypofunction following myocardial infarction, orthostatic hypotension, and elongation of internal carotid artery), and (Group D) unknown etiology--4 cases; cerebral angiography revealed no abnormalities, suggesting involvement of other factors than cerebrovascular agents.(ABSTRACT TRUNCATED AT 250 WORDS)