The diagnosis and management of patients with acute ischemic stroke still lack an informative biochemical test. Soluble glycoprotein V (sGPV) is a new plasmatic marker of thrombosis released from the platelet surface by thrombin. The objective of this prospective study was to compare the levels of sGPV in stroke and control patients. Consecutive patients with acute ischemic stroke (n=159) and controls (n=70) were recruited for sGPV measurement. Plasmatic levels of sGPV were significantly increased in ischemic stroke compared with control patients (median interquartile range 39.4 31.8 to 52.9 versus 28.1 24.0 to 37.9 ng/mL; P<0.0001). In multivariate analysis, ischemic stroke was the major determinant of the sGPV increase (odds ratio 95% CI, 5.87 2.62 to 13.12; P<0.0001). sGPV is a new marker of arterial thrombosis and represents a tool to study the mechanisms involved in ischemic stroke. The increase in plasmatic sGPV observed in stroke patients supports a role of platelets and thrombin in the events leading to ischemic stroke.