Pharmacological properties of SM-3997 (3a alpha,4 beta,7 beta,7a alpha-hexahydro-2-(4-(4-(2-pyrimidinyl)-1- piperazinyl)-butyl)-4,7-methano-1H-isoindole-1,3(2H)-dione dihydrogen citrate) have been examined in rats and mice. SM-3997 showed a dose-related anticonflict activity in rats in a water lick conflict paradigm, and it had no effect on water consumption in a spontaneous water drinking test. The potency of SM-3997 appeared to be equal to that of buspirone and about one-half that of diazepam. No tolerance to the anticonflict activity of SM-3997 was observed following 5 and 10 consecutive days of treatment. Unlike diazepam, SM-3997 had no anticonvulsant effect and had very weak muscle relaxant and hypnotic effects. On the other hand, SM-3997 and buspirone exhibited dopamine antagonistic action, although the potency of SM-3997 was less than one fourth that of buspirone. These results show that SM-3997 is a new anxioselective anxiolytic agent which is weaker than buspirone in the dopaminergic neuron system.