This study assessed potential etiologies of arterial ischemic stroke and hemorrhagic stroke among children of Mainland China. From January 1996-June 2006, 251 patients with consecutive childhood stroke (aged I month through 16 years) were admitted to Beijing Children's Hospital. Arterial ischemic stroke accounted for the majority of cases (62.5%). Idiopathic stroke (32.5%) was more common than cardiac stroke (8.9%), vascular or arteriopathic stroke (21.0%), hematologic disorder-associated stroke (10.8%), and other etiologies (26.8%). Vitamin K deficiency was a major etiology in 72 of 94 hemorrhagic strokes (76.6%), most of which occurred in breastfeeding infants (80.6%) and those who received no vitamin K after birth (73.6%). Arteriovenous malformation (6.4%) was a frequent etiology in the remaining hemorrhagic stroke cases. We found that ischemic stroke in children is more common than hemorrhagic stroke, and many cases of ischemic stroke are idiopathic. Vitamin K deficiency was a major etiology in these young infants who experienced hemorrhagic stroke. (C) 2009 by Elsevier Inc. All rights reserved.