Five subjects were sequentially heated and cooled in a double-climate chamber while mean skin temperature (except the head) and head skin temperature were separately varied. The tympanic membrane temperatures of these subjects were disproportionately influenced by changes in head skin temperature. By heating and cooling localized regions of the head, changes in tympanic membrane temperature that followed changes in skin temperature on the ipsilateral side of the head could be produced. During heating of the head, oral and tympanic membrane temperatures were influenced to a similar degree, while esophageal temperature remained essentially unaffected. However, under conditions in which the legs and feet were heated in a water bath, esophageal temperature showed more rapid changes than either tympanic membrane or oral temperature. These findings suggest that tympanic membrane temperature and, to a lesser degree, oral temperature may be affected by thermal exchange occurring between arteries and veins in the cervical and cephalic regions. In addition, the ability to influence selectively esophageal and tympanic membrane temperatures brings into question the arbitrary use of these measurements under widely different experimental conditions as estimates of core temperature.