Inclusion Criteria:

• TIA or non-severe stroke within 90 days prior to randomization (including day 90)
• Modified Rankin score of < 3
• High grade stenosis (50 to 99 percent) of a major intracranial artery (carotid artery, MCA stem (M1), vertebral artery,and basilar artery) documented by conventional angiography within 90 days prior to randomization (including day 90)
• TIA or stroke is attributed to high grade intracranial stenosis
• Age > 40 years
• Patient is able to follow an outpatient protocol(requiring monthly blood tests and clinic visits every four months for the duration of the study) and is available by telephone
• Patient understands the purpose and requirements of the study, can make him/herself understood, and has provided informed consent

Exclusion Criteria:

• Extracranial carotid stenosis (> 50 percent) ipsilateral to stenosis of the intracranial carotid artery or MCA (ie.tandem stenoses, either of which could have caused patient's symptoms)
• Isolated stenosis of the anterior cerebral artery, posterior cerebral artery, MCA division, or a distal branch of the MCA
• Intracranial or extracranial arterial dissection, Moya Moya disease, vasculitis, radiation induced vasculopathy, fibromuscular dysplasia
• Presence of any of the following unequivocal cardiac sources of embolism: chronic or paroxysmal atrial fibrillation, mitral stenosis, mechanical valve, endocarditis, intracardiac clot or vegetation, myocardial infarction within three months, dilated cardiomyopathy, left atrial spontaneous echo contrast
• A contraindication to the use of either warfarin or aspirin e.g. active peptic ulcer disease, active bleeding diathesis, platelets < 100,000*, hematocrit < 30*, clotting factor abnormality that increases the risk of bleeding, alcohol or substance abuse, severe gait instability, cerebral hemorrhage, systemic hemorrhage within the past year, severe liver impairment (SGOT > 3x normal*, cirrhosis), allergy to aspirin or warfarin, uncontrolled severe hypertension (systolic pressure > 180 mm Hg or diastolic pressure > 115mm Hg), positive stool guaiac that is not attributable to hemorrhoids, creatinine > 3.0*
• Indication for intravenous heparin beyond randomization
• A severe neurological deficit that renders the patient incapable of living independently
• Dementia or psychiatric problem that prevents the patient from following an outpatient program reliably
• Co-morbid conditions that may limit survival to less than five years
• Pregnancy or female in age range of childbearing potential who is not using contraception
• Enrollment in another study that would conflict with the current study
• Excluded because difficult to measure percent stenosis of these small arteries, lesions are uncommon, and prognosis of patients - With these lesions is unknown * on most recent test done within 90 days prior to randomization, including day 90