Estrous hamster vaginal discharge (HVD) contains both volatile and nonvolatile chemical signals which collectively elicit both male attraction to females and male mating behavior. These two aspects of normal sexual behavior are differentially affected by lesions involving afferents of the main and the accessory olfactory systems. The results of lesions that involve the main olfactory system suggest that it provides information primarily concerning those volatile components of HVD that normally signal the presence of a female. Lesions restricted to the accessory olfactory system do not impair a male's interest in or relative preference for HVD but do significantly interfere with subsequent stages of sexual behavior by reducing the amount of mating obtained upon exposure to HVD. Stimulation of the accessory olfactory system by nonvolatile components of HVD has thus been implicated in the production of mating behavior. In these experiments, male hamsters were attracted to female odor and engaged in significant amounts of mating behavior with surrogate females when only the volatile components of HVD were available to them. These behaviors were further enhanced when both volatile and nonvolatile components of HVD were provided. Lesion studies of the afferents involved reinforce the hypothesis that the main olfactory system is preferentially involved with processing those volatile chemical signals in HVD that denote female attractiveness whereas the accessory olfactory system is preferentially involved with processing those chemical signals, both volatile and nonvolatile, that evoke subsequent steps in male sexual behavior.