The present study was undertaken to examine the effects of ginseng saponins [ginseng total saponin (GTS), protopanaxadiol saponin (PD) and protopanaxatriol saponin (PT)] on the hyperactivity, reverse tolerance and dopamine receptor super-sensitivity induced by cocaine. A single treatment with cocaine produced hyperactivity. Repeated administration of cocaine developed reverse tolerance and dopamine receptor super-sensitivity was also developed in reverse tolerant mice which had received the same cocaine. The hyperactivity and the developments of reverse tolerance and dopamine receptor super-sensitivity by cocaine were inhibited by ginseng saponins. From these results, it is proposed that ginseng saponins may be useful for the prevention and therapy of the adverse actions of cocaine. In addition, the rank order of inhibitory potential was observed as PT>GTS>PD. Key words Cocaine, hyperactivity, reverse tolerance, dopamine receptor super-sensitivity, ginseng saponins.