Green tea catechins (GT-catechins) have been reported to have an antioxidative effect. We investigated the effect of long-term GT-catechin intake on aging and oxidative damage using aged mice with accelerated senescence (SAMP10), a model of brain senescence with cerebral atrophy and cognitive dysfunction. Major atrophy was observed in the rhinencephalon, hippocampus and striatum of 12-month-old untreated SAMP10 mice. Similarly, levels of 8-oxodeoxyguanosine (8-oxodG), a marker of oxidative DNA damage, were higher in these parts of the cerebrum than in the cerebral cortex and liver. GT-catechin intake effectively suppressed such atrophy in 12-month-old SAMP10 mice. A preventive effect of GT-catechin intake on oxidative DNA damage was also observed in the rhinencephalon (an area particularly susceptible to atrophy) at 6 months of age, i.e. during the early stages of atrophy. A suppressive effect of GT-catechin intake on cognitive dysfunction, as determined by the learning time needed to acquire an avoidance response and assessments of working memory in a Y-maze, was also found in 12-month-old mice. These results suggest that GT-catechin intake partially improves the morphologic and functional alterations that occur naturally in the brains of aged SAMP10 mice.