ABSTRACTIn industrialized countries about 90 % of the time is spent indoors. The environmental parameters affecting indoor thermal comfort are air temperature, humidity, air velocity and mean radiant temperature. In assessing thermal environment, besides these environmental parameters, we should also consider some personal parameters such as clothing and human activity. In this study, we tried to determine the thermal comfort factors with reference to required skin temperature (tsk,req) and sweating heat loss (Esk,req) and necessity of heat load being equal to zero. We also determined body core and mean body temperatures. Key Words : Thermal comfort, thermal comfort factors, body core and skin temperatures.