Objective: Investigation of the mechanism of the idiopathic periodic hyperthermia associated with agenesis of the corpus. callosum. Setting: Tertiary care referral center. Patient: Fourteen-year-old girl who was the first case of reverse Shapiro's syndrome (ie, agenesis of the corpus callosum associated with periodic hyperthermia, as opposed to hypothermia as described in the original report by Shapiro et al). Intervention: Magnetic resonance imaging scans, endocrinological examinations for hypothalamus, electroencephalograms, and levodopa therapy. Main Outcome Measure: Body temperature. Result: No neurologic or physical abnormalities were noted beside the callosal agenesis. Neuroimaging examinations could not reveal any structural abnormality of the diencephalon. Endocrinological examinations and electroencephalograms were found to be normal. The hyperthermia returned to normal by a small dose of levodopa, but a larger dose reversed the hyperthermia to hypothermia. Conclusions: These observations suggest that the hyperthermia observed in this case may have been caused by the dopaminergic denervation of the hypothalamic thermoregulatory center, resulting in the supersensitivity of its dopaminergic receptors.