Localization of the NOX family isoforms has been studied extensively in many tissues throughout the body. In 2001, Lambeth and his group documented strong NOX2 mRNA expression and faint RT-PCR bands of NOX4 and NOX5 in the brain (77). Moreover, further studies by our group and others revealed NOX2 (42, 69, 78) and NOX4 (79) expression in the hippocampus, as well as NOX2 localization in the cerebral cortex (78). Of the different NOX enzyme isoforms, the greatest evidence to date implicates a critical role for NOX2 in ROS generation following cerebral ischemia and the resultant oxidative stress damage. In support of this contention, infarct volume was shown to be significantly reduced in NOX2 knockout mice as compared to their wild-type litter mates (80-81). Furthermore administration of the NADPH oxidase inhibitor, apocynin was shown to reduce infarct size after FCI (82) and significantly reduced neurological deficit score in mice, thus achieving an improved behavioral cognitive outcome (80-82). The ability of apocynin to reduce infarct volume, neurological impairment and mortality was lost when it was administered in NOX2 KO mice, which strongly suggests that its beneficial neuroprotective effects are due specifically to inhibition of NOX2 NADPH oxidase (81).