“The purpose of this study was to investigate the significance of wet underwear and to compare any influence of fibre-type material and textile construction of underwear on thermoregulatory responses and thermal comfort of humans during rest in the cold. Long-legged/long-sleeved underwear manufactured from 100% polypropylene in a 1-by-1 rib knit structure was tested dry and wet as part of a two-layer clothing system. In addition cotton (1-by-1 rib knit), wool (1-by-1 rib knit), polypropylene (fishnet), and a double-layer material manufactured from 47% wool and 53% polypropylene (interlock knit) was tested wet in the clothing system. In the wet condition 175 g of water was distributed in the underwear prior to the experiment. The test was done on eight men (T(a) = 10 degrees C, RH = 85%, V(a) < 0.1 m/s), and comprised a 60 min resting period. Skin temperature, rectal temperature, and weight loss were recorded during the test. … …The tests demonstrated the significant cooling effect of wet underwear on thermoregulatory responses and thermal comfort… …The thickness of the underwear has more of an influence on the thermoregulatory responses and thermal comfort, than the types of fibres tested."