Background and Objectives ; This experimental study was conducted to evaluate an anti-stress effect of Gamisachi-tang(加味四七湯) on mice immobilized by stress. Methods : The experimental animals were immobilized by stress for 15 minutes, and administered 9mg/20g or 18mg/20g of Gamisachi-tang(加味四七湯) extract for seven days before they got stressed. The serotonin contents in the frontal cortex, hypothalamus, corpus striatum, hippocampus were measured by HPLC method in rat brain. Results : In frontal cortex, serotonin contents significantly decreased in both sample A and B group compared to the controlled group. In the hypothalamus, serotonin contents increased in both sample A and B group compared to the controlled group. In the corpus striatum, serotonin contents significantly increased in both sample A and B group compared to the controlled group. In the hippocamous, serotonin contents significantly increased in both sample A and B group compared to the controlled group. Conclusions : According to the above results, Gamisachi-tang(加味四七湯) had a significant impact on the changes in serotonin contents, which occurred in a separated part of mouse brain caused by stress.