In the first experiment, ovariectomized rats given weekly injections of estrogen and progesterone which were relatively unresponsive during preoperative testing received bilateral medial forebrain bundle (MFB) lesions. Postoperative lordosis quotients were significantly elevated. In the second experiment, MFB lesion and sham lesion rats were tested for responsiveness to decreasing doses of estrogen. Lesions had no significant effect in this experiment. In the final experiment, MFB lesions significantly increased the duration of receptivity following single injections of estrogen and progesterone. These results suggest that, like the preoptic area, under some conditions the MFB may play a role in the suppression of lordosis.