Ischemic brain injury from stroke is an important cause of disability in infants and children, but current experimental models for the disorder are complex. These preparations require occlusion of small intracerebral vessels or common carotid artery ligation combined with exposure to reduced levels of oxygen. Unilateral carotid artery ligation alone was sufficient to cause brain injury in more than 70% of 12-day-old CD1 mice. Using a blinded behavioral rating scale of seizure activity in mice, a direct, highly significant correlation between the severity of seizures over the 4-hour period after ligation and the severity of histologic brain injury 7 days later (Spearman's rho = 0.835, P < 0.001) was documented. This study presents the first model of stroke in immature mice produced by unilateral carotid artery ligation alone, and the first to demonstrate a clear correlation between acute ischemia-induced seizures and brain injury. This new model should be useful for examining the pathogenesis of stroke in the immature brain and the potential contribution of seizures to final outcome.