There are a group of so-called tonic remedies in Far Eastern medicine which are traditionally viewed as harmonizing or adjustive. Ginseng and eleutherococcus are the best known, and there is evidence that they increase arousal, stamina and stress resistance. We have attempted to explore the relationship between the behavioral and the stress effects, and to relate this to traditional concepts. In one series of experiments mice were given ginseng throughout their lifespan. At intervals their behavior response to mild stress was examined and found to be exaggerated compared to controls without ginseng. However, normal ambulatory behavior in the absence of stress was unaffected. A second series of experiments indicated that the binding of corticosteroid to certain brain regions was increased in adrenalectomized rats given ginseng saponin, compared to saline treated controls. This can be interpreted as a result of an increase in hypothalamic-pituitary-adrenal sensitivity caused by ginseng saponin. This is in accord with traditional concepts of the use of these remedies.