The endocrine correlates of sexual arousal were explored in male mice. Using indwelling atrial cannulae, temporal changes in the blood levels of six hormones were monitored in sexually rested vs. sexually sated males before and during their exposure to receptive females. The vaginae of some test females were artificially occluded to assess separately the impact of intromission on hormone levels. Sexually rested males responded to receptive females with dramatic increases in their blood levels of corticosterone, epinephrine, and norepinephrine. These changes occurred independently of intromission. Blood titers of these three hormones did not change in sexually sated males when they encountered a receptive female. Both sexually sated and sexually rested males discharged LH in a reflex-like manner immediately upon perceiving a test female. PRL was released only in response to ejaculation, and FSH titers were unaffected by the presence of a female. In general, a receptive female elicits a variety of hormonal responses in a male mouse. Some hormones seem to be discharged in response to sexual arousal per se, whereas others are released with varying degrees of independence of this process. Viewed from another perspective, the present results allow the presentation of a relatively detailed scheme that temporally relates sensory input to hormonal response during the sexual interactions of male mice.