To elucidate the preventive effect of oriental medicine Gami-Ondamtang(GO) on stress, we investigated the physiological change of rats which were applied immobilization stress. For immobilization stress, rats were placed in restrainer for 12 hours a day for 3 days. During application of stress, body weight of rats was measured. After sacrifice, 8 organs were taken for measurement of organ weight. Brain was sectioned into 4 parts that are Frontal Cortex, Corpus Striatum, Hypothalamus and Hippocampus. Each part was homogenated and its catecholamine and serotonin contents were measured with HPLC. In our study, stress mainly induced increase of concentration of neurotransmitters in brain without other significant physical change of rats. GO inhibited stress induced changes of neurotransmitter content in brain.