Ninety‐eight recordings of serial temperatures each taken at 30 sec intervals from both the dorsum of the hand and the axilla were made. A total of 23 fully clothed healthy persons at rest was monitored using an electronic thermometer with instant readout and multiple themocouple probes. Raw data were processed by a computerized program of autocorrelation for a time series analysis. The autocorrelograms indicated significant spontaneous ultradian periodicities for both hand and axillary temperatures. The cycle lengths were independent of gender, but sensitive to age. Observations of the tympanic membrane temperature and that of the nailfold on a further two subjects suggested that hypothalamic temperature oscillations of similar periodicity may be the source of the temperature rhythms of the hand and the axilla.