The underwear manufactured from 100% polypropylene was tested in two different knit constructions, a 1 -by-1 rib knit and a fishnet structure, and the woollen underwear in a 1 -by-1 rib knit construction. The test was performed on eight male subjects (Ta= I0°C, RH = 85%, Va <0-lm/s), and comprised a twice-repeated bout of 40-min cycle exercise followed by 20 min rest. Each subject conducted two tests with the work level approximating 30% [Vdot]o2 max and 40% [Vdot]o2 max, respectively. Skin temperatures, rectal temperature, #weight loss and humidity near the skin were recorded during the test. Total changes in body and clothing weight were measured separately. Furthermore, subjective ratings on thermal comfort and on sensation of temperature and humidity were collected. The results demonstrated that high heat and sweat production during work periods, leading to increased sweat accumulation, will give higher thermal discomfort ratings for rest periods as well as for work periods compared to intermittent work with lower work intensities. Distribution of accumulated sweat in the clothing ensemble after heavy sweating is dependent on the fibre type in the underwear.