In brief: The purpose of this study was to investigate the effects of using a sunscreen during exercise in both hot, dry and hot, humid environments. Sixteen men exercised for 39 minutes with sunscreen cream applied to their exposed body surface area. Results indicated that the mean skin temperature was significantly increased due to the use of sunscreen during the hot, dry exposure. This increase did not occur during the hot, humid exposure. Therefore, we concluded that using a sunscreen while exercising at low humidity retards sweat evaporation.