Transient thermal response of five types of underwear(cotton jersey, wool jersey, nylon jersey, cotton mesh and polyester mesh) for a protective coverall is evaluated using a sweating thermal manikin. Experimental protocol for transient thermal response of the sweating thermal manikin was also proposed. As results, it was found that steady state thermal response from sweating thermal manikin was not sensitive enough to evaluate thermal comfort of the experimental garments. However, when half time is used as an index of the heat flux change in transient thermal response, difference was found among underwear materials. Half time of cotton was the shortest and heat transfer of cotton was the fastest followed by polyester mesh, cotton jersey, nylon jersey and wool jersey. Dynamic thermal response of wool underwear was quite different from that of cotton underwear. Wool shows quite less heat flow at the initial stage, however, moisture permeability of wool was higher than cotton at the later stage. It was difficult to distinguish surface temperature difference visually using thermogram taken right before the completion of dry and wet test in steady state thermal response.