Following ejaculation the male rat emits a 22 kHz vocalization that has been hypothesized to play a communicative role. We found previously that this vocalization is often accompanied by rapid and selective hypothalamic cooling, and we hypothesized that the vocalization or, more precisely, the thoracic-laryngeal maneuver underlying the vocalization, is primarily a thermoregulatory behavior. Accordingly, one prediction made herein was that heating the brain of the isolated male, through the infusion of prostaglandin E2, would be accompanied by the vocalization. Another was that cooling the brain of the copulating male through the injection of sodium salicylate would significantly reduce the post-ejaculatory vocalization. Both predictions were confirmed.