We first investigated the effect of aged garlic extract (AGE) on the longevity and learning performance in the Senescence-Accelerated Mouse (SAM). A solid diet containing AGE was fed after two months of age. An AGE treatment increased the survival ratio of the SAMP8. Moreover, the preparation ameliorated the memory acquisition deficit and the memory retention impairment of the SAMP8 at 10 months old. The learning improvement was also confirmed in a spatial cognition test. We next studied the effect of AGE on another strain of the SAM, SAMP10. Although the life span prolongation was not observed in the AGE-treated SAMP10, the preparation improved the grading score, an index of aging. A surprising result was obtained by measuring the brain size. The degree of shrinkage in the frontal cerebrum was 2-9% in the SAMP10. Chronic ingestion of AGE prevented this atrophy and kept the brain size at the control level. These results suggest that AGE has an antiaging effect on the SAM.