The present experiment was desined to examine catecholamines, 5-hydroxytryptamine, amino acids, malondialdehyde(MDA) and free radical scavening activity, by administering Samultang extract of a variety of concentraction to senile brain The results were summarized as followings: 1. Samultang significantly increased noradrenaline in the cortex, striatum, hippocampus and hypothalamus of the brain tissue of senile rats, and even though Samultang increased noradrenaline also in other brain tissue, there was no significance. 2. Samultang had effects on dopamine changes in hypothalamus of the brain tissue of senile rats. 3. Samultang significantly increased 5-hydrotryptamine in pons-medulla oblongota and cerebellum, but decreased in hypothalamus. 4. Samultang increased amino acid in the brain tissue of senile rats. 5. Samultang significantly decresed lipid peroxide production in the brain tissue of senile rats. 6. Samultang significantly decresed MDA and free radical in the brain tissue of senile rats. According to the above results, Samultang is assumed to improve brain function by reacting on biochemical of the senile brain, and that Samultang can be used to treat regressive brain disease carrying symptoms of psychoactive disorders.