Nineteen patients between 56 and 76 years of age with clinically symptomatic atherosclerotic stenotic lesions at or distal to the C-5 segment in the carotid arterial system underwent percutaneous transluminal angioplasty (PTA). The 19 patients had a total of 19 stenotic lesions, including two lesions in the C-5 segment, three in the C-4 segment, and three in the C-2 segment of the carotid artery, six in the M1 segment and three in the M2 segment of the middle cerebral artery, and two in the A2 segment of the anterior cerebral artery. Both prior to and more than 6 months after PTA, angiograms were performed and cerebral perfusion was measured using 99mTc-hexamethyl-propyleneamine-oxime single-photon emission computerized tomography, before and after the administration of 10 mg/kg acetazolamide. Percutaneous transluminal angioplasty could be performed in 13 (68.4%) of the 19 patients. The mean degree of stenosis (+/- standard deviation) was 83.1% +/- 8.6% before PTA, but only 35.8% +/- 17.3% on the follow-up angiograms. Restenosis was detected in follow-up angiograms in five (38.5%) of the 13 patients. Seven of the 13 patients exhibited improvement in their neurological condition after PTA and had shown subnormal cerebral perfusion and subnormal vasodilatory response to administration of acetazolamide prior to undergoing PTA. On the other hand, the remaining six patients exhibited no improvement in neurological condition after PTA, and four of these patients (66.7%) had shown normal perfusion and five (83.3%) had shown normal vasodilatory response to administration of acetazolamide prior to undergoing PTA. These findings suggest that PTA may be indicated for patients with atherosclerotic stenotic lesions in the anterior cerebral circulation who have subnormal cerebral perfusion and low vasodilatory response to administration of acetazolamide.