The sexual behavior of 18 female and 11 male rhesus monkeys was observed in pair tests, in two experiments. In one experiment the females controlled the occurrence of pair tests. The females were ovariectomized and treated with estradiol, two dosages of testosterone, estradiol plus testosterone, estradiol plus dexamethasone, or no hormone; and the effects of the treatment on female attractiveness, proceptivity, and receptivity were examined. Sexual attractiveness of females to males (the effectiveness of the female as a sexual stimulus) was affected by estrogen and androgen. Estrogen enhanced attractiveness, but the effect of androgen depended on the dose. Female sexual proceptivity (the extent to which the female seeks out the male and elicits sexual behavior) was heightened by estrogen and androgen. Female sexual receptivity (willingness to receive a male in copulation was somewhat stimulated by estradiol, but not by testosterone. Both estradiol and testosterone had a greater effect on attractiveness and proceptivity than on receptivity. The hypothesis that testosterone is the "libidinal hormone" in female primates was not supported.