Aspirin Or Warfarin To Prevent Stroke

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 cardio…