The proposed research tests the hypothesis that decreases in the space available for social interaction increases the probability of sexual activity occurring in heterosexual pairs of rhesus monkeys (Macaca mulatta), thus masking or altering the influence of the female's hormonal state on the display of sexual behavior. Intact female rhesus and vasectomized male rhesus will be observed sequentially in a 3 x 5 ft cage and in a 50 X 50 ft compound during the follicular and luteal phases of the menstrual cycle. Ovariectomized rhesus will be tested under the same spatial conditions when hormonally untreated and during treatment with estradiol benzoate. Data will be collected using an electronic keyboard which preserves the sequential occurrence of specific behavioral patterns as well as providing durations and frequencies. The proposed research specifically investigates the effect of space and the female's hormonal state upon behaviors thought to be indicative of male and female sexual solicitation as well as behavioral patterns involved in copulation and affiliation. The proposed research is the first systematic investigation of the influence of spatial factors on the display of sexual behavior in a nonhuman primate and represents the first step towards describing the interaction between the female's hormonal state and environmental factors on the expression of primate sexual behavior. In addition, this research will provide a bridge between laboratory and semi-field studies of hormonal influences upon female rhesus sexual behavior and help reconcile differences in results obtained from these two research environments. It is felt that investigation of the influence of social, environmental, and hormonal influences upon sexual behavior in a nonhuman primate offers the best hope of providing a meaningful context to study questions relevant to hormonal influences on human sexual behavior.