The role of the vomeronasal organ (VNO) in the male-induced enhancement of sexual receptivity in ovariectomized estrogen-primed rats was investigated. Removal of the VNO significantly reduced the enhancement of sexual receptivity following mating, as compared with the sham-operated controls. The sham-operated females exhibited a surge of luteinizing hormone (LH) following mating; however, LH release induced by pairing with males was less manifested in the VNO-removed females. This suggests that in female rats, VNO removal impairs the male-induced release of LH-releasing hormone (LHRH). Since LHRH enhances sexual receptivity in ovariectomized estrogen-primed rats, the present results suggest that the increase in sexual receptivity in female rats following mating probably results from a VNO-mediated LHRH release.