Earlier studies suggest that α 2 -adrenoceptor antagonists and dopamine receptor agonists may enhance sexual activity in human and nonhuman male primates. It is not known whether these compounds influence the sexual behavior of female primates. We determined whether the administration of a selective α 2 -adrenoceptor antagonist (atipamezole), a dopamine receptor agonist (apomorphine), or their combination to female Macaca arctoides (stumptail macaque) monkeys produces changes in sexual behavior of the female with a male. Following the administration of drugs to the female, the behavior of the female with a male stumptail was observed for 30 min. Atipamezole dose dependently (0.03–0.3 mg/kg im) increased short-time mounting behavior of the male and the total number of copulations. Apomorphine alone (0.125–0.25 mg/kg) or in combination with atipamezole had no significant effects on sexual behavior. The result indicates that a selective α 2 -adrenoceptor antagonist administered in the female stumptail increases sexual behavior of the male with the female. A plausible explanation for this finding is that a selective α 2 -adrenoceptor antagonist increases sexual arousal in female stumptails and this, possibly due to a change in psychosocial behavior of the female, triggers increased sexual activity in males.