Objective To investigate the levels and its clinical significance of activated platelets in patients with transient ischemic attack(TIA). Methods Color Doppler flow imaging was used to measure the degree of carotid atherosclerosis in 72 patients with TIA(TIA group). Flow cytometry (FCM) was used to measure the levels of PAC-1 and CD62P. They were compared with 30 healthy controls(NC guoup). Results The levels of PAC-1 and CD62P in TIA group were significantly higher than those in NC group (allP