Activities of monoamine oxidase B, Cu-Zn-dependent superoxide dismutase (SOD), and catalase, and concentration of enzyme-active ceruloplasmin were measured in brain preparations from 43 humans died at the age of 21-92 years. Activity of monoamine oxidase B in the neocortex, cerebellum, basal ganglia, and stem structures increased with age, while SOD activity decreased and catalase and ceruloplasmin concentrations slightly increased. A contribution of age-related increase of cerebral monoamine oxidase activity into ontogenetic impairment of the antioxidant defense in human brain is discussed.