Exercise increases heat production. During exercise in both warm and cold conditions, the major dilemma is the dissipation of the heat produced from muscular activity. The use of clothing generally represents a layer of insulation and as such imposes a barrier to heat transfer and evaporation from the skin surface. In warm environments, additional clothing increases thermal insulation causing more rapid increases in temperature during exercise and imposes a barrier to sweat evaporation. However, clothing can serve a protective function by reducing radiant heat gain and thermal stress. Recent research suggests that neither the inclusion of modest amounts of clothing nor the clothing fabric alter thermoregulation or thermal comfort during exercise in warm conditions. In the cold, most reports do not support an effect of clothing fabric on thermoregulation; however, there are reports demonstrating an effect. Clothing construction does alter thermoregulation during and following exercise in the cold, where fishnet construction offers greater heat dissipation. Future research should include conditions that more closely mimic outdoor conditions, where high work rates, large airflow and high relative humidity can significantly impact thermoregulation.