This study aimed to evaluate the anti-stress effect of Yangsimtang and Yangsimtang+Siyup on the rats in immobilization stress.The experimental animals were immobilized in the stress box(5${ imes}$5${ imes}$20cm) for 12 hours in a day suring 3 days, and administered 1ｇ/100ｇ of Yangsimtang and Yangsimtang+Siyup and Siyup extract for 12 days before stress. The norepinephrine, epinephrine, dopamine and serotonin contents were measured by HPLC method in various part of rat brain.The following results were observed.1. In frontal cortex the norepinephrine content of control group was 561.${pm}$24.46 ng/g brain tissue, that of saple 1 group was 430.8$pm$41.2 ng/g brain tissue, and that of sample 2 group was 417.2$pm$38.5 ng/g brain tissue. The differences was statistically significant.2. In corpus striatum, the norepinephrine content of control group was 561.3$pm$27.3 ng/g brain tissue, and that of sample 1 group was 422.1$pm$21.2 ng/g brain tissue, the dopamine content of control group was 1205.1$pm$75.9 ng/g brain tissue, that of sample 2 group was 685.6$pm$41.5 ng/g brain tissue. The differences was statistically significant.3. In hypothalamus, the norepinephrine content of control group was 1165.1$pm$162.6 ng/g brain tissue, that of sample 2 group was 947.2$pm$35.7 ng/g brain tissue. The differences was statistically significant.4. In hippocampus, the norepinephrine content of control group was 931.6$pm$82.2 ng/g brain tissue, that of sample 1 group was 652.1$pm$47.5 ng/g brain tissue, and that of sample 2 group was 627.4$pm$31.2 ng/g brain tissue, the dopamine contrnt of control group was 315.4$pm$28.4 ng/g brain tissue, that of sample 2 group was 208.5$pm$23.7 ng/g brain tissue. The differences were statistically significant.Base on the above results, it may be concluded that Yangsimtang and Yangsimtang+Siyup are effective to reduce stress.