Daytime restriction of food and water availability in nocturnal animals phase-shifts the circadian periodicity of plasma corticosteroid concentrations and body temperature. These shifted rhythms do not persist in animals with lesions of the ventromedial hypothalamus, in contrast to our previous reports of persistence of such shifted rhythms in animals with lesions of the suprachiasmatic nuclei. These findings suggest that the ventromedial hypothalamus may be the anatomical locus which mediates the circadian response to food synchronization.