Diazepam and chlordiazepoxide produced a dose-dependent inhibition of ambulatory activity, motor execution and sexual behavior. The benzodiazepine antagonist flumazenil had no effect on these behaviors, while the inverse agonist FG 7142 inhibited sexual behavior without affecting motor functions. The GABA antagonist bicuculline was ineffective in all behavioral paradigms, while picrotoxin inhibited all behaviours. Picrotoxin blocked the motor effects of low doses of the benzodiazepines, but not those of higher doses. Neither did this drug block the effects of benzodiazepines on sexual behavior. Bicuculline was unable to block the effects of benzodiazepines on all behaviors. FG 7142, in a low dose, inhibited the effects of diazepam and chlordiazepoxide on ambulatory activity, but not their effects on motor execution or sexual behavior. The effects of the benzodiazepines and picrotoxin on sexual behavior could be a consequence of the motor impairment produced by these drugs, since the doses required to effect these two behaviors were similar. However, the fact that picrotoxin could block the motor deficiencies induced by the benzodiazepines without restoring sexual behavior suggests that these behavioral actions of the drugs can be differentiated. While some evidence was obtained suggesting a role of GABA in the motor effects of benzodiazepines, no evidence could be found for a role of GABA in their effects on sexual behavior.