Clopidogrel is an anti-platelet agent used to inhibit blood clots. Variation in response to clopidogrel has been reported among different population and may lead to reoccurring ischemic events. The aim of the present study is to evaluate the incidence of clopidogrel resistance in ischemic stroke patients from different ethnicities in Northern Israel and to find different strategies to overcome high platelet reactivity including clopidogrel dose adjustment or the choice of alternative agents. Quantification of platelet aggregation will be determined by vasodilator stimulated phosphoprotein (VASP) assay.

Inclusion Criteria:

1. Ability to provide written informed consent and to be compliant with protocol assessments.
2. Ages 18 and above inclusive
3. Both genders eligible for the study
4. Diagnosis of ischemic cerebrovascular event

Exclusion Criteria:

1. Pregnant patients will be excluded
2. Ages below 18
3. Patients not able to provide informed consent

This prospective study will be conducted in two sites (Ziv Medical Center, Safed, department of neurology, and Galilee Medical Center, Nahariya, department of neurology) on 300 patients from different ethnic backgrounds with an ischemic cerebrovascular event (ischemic stroke and TIA), treated with clopidrogel for secondary stroke prevention. The groups will consist of Jewish communities (Ashkenazi, Sephardi and Ethiopian) and Arab populations (Muslim, Christian and Druze).

To be considered eligible to participate in this study, patients have to be able to provide signed and dated written informed consent or written assent from their relatives. Both genders aged 18 and above are eligible for this trial. Pregnant patients will be excluded.