Following extensive preoperative tests in which 234 male Sprague-Dawley rats were run to sexual exhaustion, bilateral electrolytic lesions were placed in 8 areas of the diencephalon and rhinencephalon to investigate their role in the mediation of sexual behavior. Postoperative tests indicate that lesions in the medial preoptic-anterior hypothalamic region completely abolished copulatory and ejaculatory behavior in 11 of 17 Ss while leaving precopulatory sexual arousal intact. Lesions in the stria terminalis and basomedial-corticomedial amygdala resulted in an increase in the time spent responding to ejaculation (i.e., time from initial mount with thrust, in an ejaculation series, to ejaculation) and a slight reduction in the number of ejaculations to exhaustion. (20 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)