The correlation between Al metabolism and senile dementia in animal has been studied by AMS (accelerator mass spectrometry). Three groups of laboratory rats were fed with normal food, food with high Al content, and with enriched Ca and Mg together with high Al, respectively for six to eight months. Mapping test was made to record the degree of wisdom degeneration. Half of the rats were sacrificed and Al contents in various organs were measured by atomic absorption spectroscopy. The rest were injected with ²⁶Al, killed after 5, 10, 15, 25, and 35 d and ²⁶Al contents measured by AMS. The distribution of Al as well as the correlation among the accumulation of ²⁶Al, and the existed Al content and dementia was studied.