The presence of reduced blood flow and increased oxygen extraction fraction (OEF) (misery perfusion) in the hemisphere distal to an occluded carotid artery is a proven risk factor for subsequent stroke. Whether angioplasty of intracranial stenosis is sufficient to reverse this condition has not been documented. A 67-year-old man exhibited progressive right hemispheric ischemic symptoms despite maximal antiplatelet and antithrombotic therapy. Angiography demonstrated focal 80% stenosis of the supraclinoid segment of the ipsilateral internal carotid artery. 15O positron emission tomographic measurements of cerebral blood flow and OEF were made before and after transfemoral percutaneous angioplasty. OEF values measured before angioplasty were elevated in the middle cerebral artery distal to the stenosis. Angioplasty reduced the degree of luminal stenosis to 40% (linear diameter). OEF values measured 36 hours after angioplasty were normal. Angioplasty of intracranial stenosis can restore normal cerebral blood flow and oxygen extraction, despite mild residual stenosis after the procedure. Hemodynamic measurements may be useful for the identification of patients with the greatest potential to benefit from angioplasty.