Reflexive ovulation in the rat, induced by caesarian section performed on day 22 of pregnancy, was blocked by prior bilateral transection of the pelvic and/ or hypogastric nerves, which convey afferent activity from the reproductive tract. Tubal ova and hemorrhagic ovarian follicles were counted 24 h after bilateral nerve transections or sham neurectomy. Whereas the median numbers of ova and hemorrhagic follicles in the sham neurectomy group were 4.5 and 3.5, respectively, these values in each of the neurectomy groups were 0. The present findings indicate that caesarian section activates the pelvic and hypogastric nerves to trigger ovulation. This suggests that normally the rat is a spontaneous ovulator during the estrous cycle (nonpregnancy) phase of its reproductive cycle, and may become a reflexive ovulator at the parturient phase of its reproductive cycle.