BASE is a multisite prospective study with a estimated enrollment of up to 1100 subjects adult subjects and 100 age, gender and co-morbidity matched controls ("Controls") will be recruited from patients who present to the Emergency Department (ED) or hospital with suspected AIS or TIA. Research personnel will identify potential patients by responding to "Brain Attacks" pages from the ED to the Stroke Team for patients who meet current Brain Attack criteria. Following evaluation by the ED and neurology physicians, the clinical coordinator will verify the patient had a suspected AIS or TIA and meets eligibility criteria. The patient or their legal surrogate will be approached for study participation. Written informed consent will be obtained for all subjects enrolled.