The objectives of this study were to examine the effects of olfactory cues from the male and of olfactory bulb removal on early mating behavior in sexually inexperienced diestrous female rats primed with estrogen. Four-day cyclic rats isolated from the male were given either 2.5 micrograms or 10 micrograms estradiol benzoate (EB) and presented to stimulated males in the late afternoon of diestrus 2 between 18:00 and 19:00 for a 10 min sexual behavioral session. Dose-dependent effects of estrogen were observed since 10 micrograms EB significantly increased the proportion of females displaying early mating as compared with those given 2.5 micrograms EB. Olfactory bulb removal prior to estrogen treatment caused a rise in the number of females which mated early with respect to the non bulbectomized controls. Exposing the females to bedding soiled with male urine on diestrus 2 at 10:00 did not affect early mating behavior. By contrast the olfactory stimuli became efficient when 2.5 micrograms EB treated females were given 10 micrograms progesterone (P) by the time of exposure to male urine. The results were discussed with respect to the role played by the olfactory system in the control of lordosis behavior throughout estrous cycle in female rats. P was concluded to be involved in the perception of the olfactory signals from the male which facilitate early mating behavior in diestrous female rats.