The actual clothing conditions of male collegian were surveyed to analyse clothing contents and the rate of wearing underwear. Then, clothing microclimate, physiological responses, and subjective sensations were investigated through wearing trials on human body in climatic chamber based on the results from the survey. The results were follows: 1. Male collegian wore T-shirts, jeans, and socks in summer, and total clothing weight per body surface area was $561g/m^2$. The number of clothes for upper body were 1 layer, but the number of clothes for lower body were 2 layers. Subjective sensations have no significant difference with wearing underwear. 2. Most physiological responses including temperature inside clothing, mean skin temperature, skin temperature of chest, abdomen, thigh, and lower leg, and sweat rate, were higher in with-underwear than in without-underwear. But pulse rates were not significantly different between with-and without-underwear.