Carotid Occlusion Surgery Study

Inclusion Criteria: * Vascular imaging demonstrating occlusion of one or both internal carotid arteries. * Transient ischemic attack (TIA) or ischemic stroke in the hemispheric carotid territory of one occluded carotid artery. * Most recent qualifying TIA or stroke occurring within 120 days prior to projected performance date of PET. * Modified Barthel Index \> 12/20 (60/100). * Language comprehension intact, motor aphasia mild or absent. * Age 18-85 inclusive. * Competent to give informed consent. * Legally an adult. * Geographically accessible and reliable for follow-up. Exclusion Criteria: * Non-atherosclerotic carotid vascular disease. Blood dyscrasias: Polycythemia vera ,essential thrombocytosis, sickle cell disease (SS or SC). * Known heart disease likely to cause cerebral ischemia (echocardiography not required). This includes the following conditions ONLY: Prosthetic valve, Infective endocarditis, Left atrial or ventricular thrombus, Sick sinus syndrome, Myxoma, Cardiomyopathy with ejection fraction \<25%. This is an all-inclusive list. The following conditions are NOT EXCLUSIONS: Atrial fibrillation, patent foramen ovale, atrial septal aneurysm. * Other non-atherosclerotic condition likely to cause focal cerebral ischemia. * Any condition likely to lead to death within 2 years. * Other neurological disease that would confound follow-up assessment. * Pregnancy. * Subsequent cerebrovascular surgery planned which might alter cerebral hemodynamics. * Any condition which in the participating surgeon's judgment makes the subject an unsuitable surgical candidate. * Participation in any other experimental treatment trial. * Participation within the previous 12 months in any experimental study that included exposure to ionizing radiation. * Acute, progressing or unstable neurological deficit. Neurological deficit must be stable for 72 hours prior to the performance of PET. * If supplemental arteriography is required, allergy to iodine or x-ray contrast media, serum creatinine \> 3.0 mg/dl or other contraindication to arteriography. * If aspirin is to be used as antithrombotic therapy in the perioperative period, those with allergy or contraindication to aspirin are ineligible. * Medical indication for treatment with anticoagulant drugs, ticlopidine, clopidogrel or other antithrombotic medications such that these medications cannot be replaced with aspirin in the perioperative period as deemed necessary by the COSS neurosurgeon if the participant is randomized to surgical treatment. * Remediable medical conditions. Patients with the following conditions can become eligible if the exclusion criterion no longer applies within 120 days of onset of the most recent qualifying event: Uncontrolled diabetes mellitus (FBS \> 300 mg%/16.7 mmol/L), Uncontrolled hypertension (systolic BP\>180, diastolic BP \>110), Unstable angina, Uncontrolled hypotension (diastolic BP \< 65).