Platelet activation plays an important role in atherothrombotic disease. Several glycoproteins are expressed on the platelet surface during platelet activation. One of them is P-selectin (CD62P), the more important platelet activation marker. P-selectin is transmembrane protein of the α-granules, which is translocated to the cell surface following activation. The interaction between platetel P-selectin and the specific ligand for P-selectin on leukocytes, P-selectin glycoprotein ligand-1 (PSGL-1), resulting in the formation of platelet-leukocyte complexes, and secretion cytokines and chemokines leading to aggravate the inflammatory processes. Glycoprotein 53 (CD63) which is present in lysosomal membranes also translocates to the plasma membrane during platelet activation. Platelet hyperactivation has been reported in patients with ischemic stroke. Several studies have suggested that platelets are excessively activated in the acute and chronic phases after cerebral ischemia. Therefore, finding platelet function test, could be the first step toward identifying patients who would benefit from antiplatelet treatment.