The purpose of this study was to determine the validity of non-contact infrared thermometry to measure mean skin temperature in resting and exercising subjects in cold, thermo-neutral and hot environments. The subjects for the study were six healthy volunteers. Skin temperature was measured at three sites: the forearm, chest and calf on each subject using both contact thermistors and a non-contact infrared thermometer. Data were collected at rest and during exercise in three different air temperatures (15, 25 and 35 degrees C). The correlation of resting mean skin temperature using infrared thermometry and contact thermistors was r = 0.95, while the correlation obtained during exercise was r = 0.98. The results of the current study strongly suggest that infrared thermometry is a valid measure of skin temperature during rest and exercise in both hot and cold environments. It is hoped that the results of this study will encourage the use of non-contact infrared thermometry by both clinicians and exercise, environmental, and sleep researchers in the future.