This study was undertaken to estimate whether nalbuphine, a mixed agonist/antagonist opioid analgesic produced psychic dependence. Moreover, the physical dependence liability of nalbuphine was compared with that of morphine after 7 days administrations of the drugs in mice and rats, and the effects of ginseng total saponin (GTS) on the development of physical dependence on nalbuphine were also studied. Nalbuphine did not produce psychic dependence. However, various abstinence signs precipitated by naloxone were observed in nalbuphine-dependent mice and rats. As the nature of the dependence syndrome produced by nalbuphine 30 mg/kg under these conditions seems similar to that induced by morphine 10 mg/kg, it is clear that nalbuphine possesses the substantial abuse potential. Therefore, nalbuphine may be needed to initiate more stringent controls for the prevention of nalbuphine abuse. On the other hand, GTS inhibited the development of physical dependence on nalbuphine and reduced the contents of dopamine and its metabolite in the brains of mice. Accordingly, results of this study suggest that the inhibitory effects of GTS on the development of physical dependence on nalbuphine may involve dopaminergic mechanism. GTS may be useful for the therapy of physical dependence on nalbuphine.