Caveolins (Cav), the principal structural proteins of the caveolar domains, have been implicated in the pathogenesis of ischemic injury. Indeed, changes in caveolin expression and localization have been reported in renal and myocardial ischemia. Genetic ablation of the Cav-1 gene in mice was further shown to increase the extent of ischemic injury in a model of hindlimb ischemia. However, the role of Cav-1 in the pathogenesis of cerebral ischemia remains unknown. Immunoblot and immunofluorescence analyses of rat brains subjected to middle cerebral artery occlusion revealed marked increases in endothelial Cav-1 and Cav-2 protein levels. To directly assess the functional role of caveolins in the pathogenesis of cerebral ischemic injury, we next investigated the effects of cerebral ischemia in caveolin knockout (KO) mice. Interestingly, Cav-1 KO mice showed a marked increase of cerebral volume of infarction, as compared with wild-type and Cav-2 KO mice. Immunofluorescence analyses showed an increased number of proliferating endothelial cells in wild-type ischemic brains, as compared with Cav-1 KO ischemic brains. Immunoblot analyses of wild-type ischemic brains showed an increase in endothelial nitric oxide synthase protein levels. Conversely, the protein levels of endothelial nitric oxide synthase remained unchanged in Cav-1 KO ischemic brains. TUNEL analysis also showed increased apoptotic cell death in Cav-1 KO ischemic brains, as compared with wild-type ischemic brains. Our findings indicate cerebral ischemia induces a marked increase in endothelial Cav-1 and Cav-2 protein levels. Importantly, genetic ablation of the Cav-1 gene in mice results in increased cerebral volume of infarction. Mechanistically, Cav-1 KO ischemic brains showed impaired angiogenesis and increased apoptotic cell death.