Superoxide dismutase (SOD) is one of the most effective mechanisms in physiology for inactivating reactive oxygen species. Elevated SOD activity can be therapeutically useful by protecting against oxidative stress-induced neurotoxicity. Acutely increased extracellular-SOD (EC-SOD) activity protects against neurobehavioral impairment caused by acute ischemia. Chronically increased EC-SOD activity may also be therapeutically useful by protecting against chronic oxidative stress-induced neurobehavioral damage that accumulates during the aging process. We have found that mice with genetic overexpression of EC-SOD do not show the aging-induced decline in learning and memory that control, wild type mice show. From 14-22 months of age, the EC-SOD overexpressing mice have significantly better spatial learning working memory function than that of controls. This effect is specific to the aging period. Young adult EC-SOD overexpressing mice do not have better learning and memory function than controls. The beneficial effects of increased EC-SOD activity with aging may be achieved without risk of impairment during younger ages by chronically administering EC-SOD mimetics from mature adulthood into the aging period. Novel EC-SOD mimetics may be useful in attenuating aging-induced cognitive impairments and other aspects of physiological decline with aging.