The results of behavioral studies suggest specific roles for high-frequency vocalizations (ultrasounds) in courtship and copulatory interactions among golden hamsters. In addition, these results, and functional interpretations based on them, can help to guide studies of physiological mechanisms controlling ultrasonic communication. For example, interpretations of rodent ultrasounds as sexual or agonistic signals suggest that ultrasound rates depend on gonadal hormones. This prediction has been verified for several rodent species, including hamsters. Similar reasoning should apply to the analysis of brain mechanisms for ultrasound production. In particular, the consideration of hamster ultrasounds as sexual behaviors and vocalizations, as well as hormone-dependent responses, suggests several brain areas as especially likely participants in neural circuits mediating hormonal effects on ultrasonic communication. The preliminary results of a study in which we lesioned one of these areas, the mesencephalic central grey, confirm this structure's involvement in the control of hamster ultrasounds, and, more generally, support the utility of behavioral data in physiological studies.