SUMMARY

The behavioural interactions between pairs of oppositely sexed, adult rhesus monkeys were studied during 1307 mating tests, each of 1 hr. dura-tion. Females were ovariectomized and the effects of administering oestrogen subcutaneously, intravaginally, and directly to the sexual skin at different daily dose rates were compared. The subcutaneous route resulted in a greater enhancement of the overall sexual activity of the pair, and in a greater stimulation of the females ' sexual invitations. In contrast, the intravaginal route of administration resulted in a greater stimulation of the males ' sexual interest and of the males ' mounting attempts: this occurred without a corresponding increase in female sexual receptivity and, in two pairs, resulted in increased aggression. It is concluded that communication between these primates was influenced by oestrogen-dependent changes in the vagina, and the findings point to the existence of a substance with a pheromone-like action