The sexual behavior of rhesus monkeys in 15 male-female pairings was observed in both a large and a small area during the follicular and luteal phases of the female's cycle. Males ejaculated in all tests at the follicular phase of the female's cycle and in 53 percent of tests at the luteal phase. However, a significant decline in ejaculation during tests at the luteal phase occurred in the large, but not in the small area. Thus the degree to which the pair's sexual behavior was influenced by the female's hormonal state depended on the spatial conditions of the test.