Effects of the Panax ginseng root (PGR) on spontaneous motor activity (vertical and horizontal motor activities), and on monoamine-related substances (tyrosine, DA, DOPAC, 3-MT, HVA, NE, MHPG, tryptophan, 5-HT, and 5-HIAA) in discrete brain areas (cerebral cortex, hippocampus, hypothalamus, corpus striatum, limbic lobe, midbrain, cerebellum, and medulla oblongata) of ddY male mice (weighing 18-22 g) were examined using an infrared photo-cell counter and HPLC with electrochemical detection. PGR (100 mg/kg) was orally administered, twice a day, for 2 successive weeks (2W-group) or 7 successive weeks (7W-group). Vertical and horizontal motor activities increased significantly in the 7W-group but not in the 2W-group when compared to those of the control group. As to brain monoamine-related substances, the metabolism of DA and NE in the cerebral cortex and of 5-HT in the corpus striatum and cerebellum in the 2W-group were facilitated, while metabolism of DA in the corpus striatum and of 5-HT in the hypothalamus and midbrain were inhibited. In the 7W-group, except for a facilitated metabolism of 5-HT in the cerebellum, metabolism of DA, NE and 5-HT in all discrete brain areas were inhibited. These results show that PGR exerts an influence on the CNS.