We studied the effect of Saiko-ka-ryukotsu-borei-to (crude extract powder for research purposes) on central monoamine-related substances in mice. The formulation was given in a dose of 50mg/kg or 400mg/kg and was administered once or repeatedly (twice a day for seven days). The brain was removed and segmented in the conventional method. The monoamine-related substances were measured by a method using HPLC-ECD. The main results were as follows. The single or repeated administration of 50mg/kg increased DOPAC and HVA contents in the cerebral cortex. In the hypothalamus, the single 50mg/kg treatment decreased NE, and the repeated 50mg/kg treatment decreased NE but increased DOPA. In the corpus striatum, the single 50mg/kg administration increased DA, DOPAC, HVA, and 5-HIAA while the repeated administration increased NE and MHPG as well. In this region, the single 400mg/kg treatment increased NE and 5-HIAA, and the repeated treatment increased NE. In the hyppocampus, the repeated 50mg/kg treatment increased MHPG, and the repeated 400mg/kg treatment decreased HVA. These results indicate that the effect of this formulation on murine brain monoamines is greater at 50mg/kg than at 400mg/kg and that the effect varies among the regions of the brain.