The administraction of ginseng butanol fraction(GBF) inhibited the development of tolerance to and physical dependence on morphine induced by morphine multiple injections in mice. Each group of mice was injected with morphine hydrochloride (40mg/kg s.c.) three times at 8 hr intervals for a period of 6 days. GBF (25, 50, 100, 200mg/kg) was injected (i.p.) to mice 1hr prior to the third morphine injection daily. Inhibition of morphine tolerance by GBF was evidenced by the increase in analgesic response to morphine hydrochloride (10mg/kg) as estimated by the tail flick method and the reduction in morphine dependence was estimated by the decreased number of the naloxone induced withdrawal jumping mice. Further evidenced that GBF reduced the development of morphine dependence was indicated by the fact that GBF decreased the loss in body weight.