Inclusion Criteria1. Ischemic cerebral infarction or TIA within 90 days.
2. Aged above 40 years old.
3. Cranial CT or MRI scan exclude intracranial hemorrhagic diseases
4. Stable clinical and neurological conditions.
5. Informed consent is obtained.
Exclusion Criteria1. Intracranial hemorrhage
2. Stroke of other unkonwn causes, or other known causes, such as Takayasu arteritis, Moyamoya disease, dissecting aneurysm and hypercoagulable state, carotid endarterectomy, angiogram, or cardiac surgery
3. Cardio embolism
4. Patients with anticoagulants treament including heparin or warfarin
5. Severe co-morbid or unstable medical condition, ie, heart failure, respiratory failure and renal failure, severe liver dysfunction, malignancy with likelihood of death within the next 2 years
6. Significant memory or behavioural disorder, ie, Alzheimer disease, etc, daily care needed.
7. A Modified Rankin score is more than 4
8. Abnormal liver function: ALT or AST level ＞1.5 times upper limit of normal; Abnormal renal function: serum creatinine level ＞2.0mg/dl or 177umol/l:
9. Concurrent participation in another clinical trial
10. Uncontrolled hypertension : systolic blood pressure greater than 180mmHg, or diastolic blood pressure greater than 100mmHg
11. Haemostatic disorder or thrombocytopenia (i.e., PLT＜100×109/l).
12. Currently active peptic ulcer disease
13. Pregnant or breast feeding
14. Planned for major surgery, carotid endarterectomy, or carotid angioplasty
15. Unable to give informed consent.