The present experiment was designed to examine catecholamines, serotonine, amino acids, malondialdehyde and free radical scavenging activity, by administering Yukmijihwangtang extract of a variety of concentraction to senile brain. The results were summarized as followings: 1. Yukmijihwangtang significantly increased noradrenaline in the striatum, hypothalamus, midbrain and pons-medulla oblongota of the brain tissue of senile rats, and even though Yukmijihwangtang increased noradrenaline also in other brain tissue, there was no significance. 2. Yukmijihwangtang significantly increased dopamine in the striatum, hypothalamus and midbrain of the brain tissue of senile rats, and even though Yukmijihwangtang increased dopamine also in other brain tissue, there was no significance. 3. Yukmijihwangtang significantly increased serotonine in the pons- medulla oblongata and cerebellum of the brain tissue of senile rats, and even though Yukmijihwangtang increased serotonine also in the other brain tissue except hypothalamus and midbrain, there was no significance. 4. Yukmijihwangtang significantly increased amino acid in the brain tissue of senile rats. 5. Yukmijihwangtang significantly decresed malondialdehyde and free radical in the brain tissue of senile rats. According to the above results, Yukmijihwangtang is assumed to improve brain function by reacting on biochemical of the senile brain, and that Yukmijihwangtang can be used to treat regressive brain disease carrying symptoms of psychoactive disorders.