Extracellular adenosine critically modulates ischemic brain injury, at least in part through activation of the A1adenosine receptor. However, the role played by the A2Areceptor has been obscured by intrinsic limitations of A2Aadenosinergic agents. To overcome these pharmacological limitations, we explored the consequences of deleting the A2Aadenosine receptor on brain damage after transient focal ischemia. Cerebral morphology, as well as vascular and physiological measures (before, during, and after ischemia) did not differ between A2Areceptor knock-out and wild-type littermates. The volume of cerebral infarction, as well as the associated neurological deficit induced by transient filament occlusion of the middle cerebral artery, were significantly attenuated in A2Areceptor knock-out mice. This neuroprotective phenotype of A2Areceptor-deficient mice was observed in different genetic backgrounds, confirming A2Areceptor disruption as its cause. Together with complimentary pharmacological studies, these data suggest that A2Areceptors play a prominent role in the development of ischemic injury within brain and demonstrate the potential for anatomical and functional neuroprotection against stroke by A2Areceptor antagonists.