Deaths from thermal stress have been reported in saunas, diving environments, and now hot spa baths. While investigating the physiological effects of hyperthermic immersion and its application to the therapy of hypothermia, some disturbing physiological anomalies were noted in normal subjects. The effects of standing, cold water immersion and of exercise, each following hyperthermic immersion, were examined. This was a pilot study only but it now seems possible that the ectopic beats may be an effect of the hyperthermic environment rather than the return of cold blood to the extremities, as previously assumed.