The purpose of this study was to evaluate the buffering capacity against water vapor of fabrics by using an apparatus that simulated the human-clothing-environment system. The influence of the hydrophilicity of fabrics, thickness of air layer and air flow on the buffering capacity were analyzed. The wear trials were performed to examine whether the buffering capacity index could work as an index to predict the subjective comfort sensation. Polyester and cotton fabrics were used as specimens. The changes of humidity and temperature of air layer in the simplated system were measured and the buffering indices K , K and $eta$ were determined by considering , , , and tant$eta$. Results showed that buffering index for polyester was higher than cotton. As the thickness of air layer increased, buffering capacity increased. When there was an air current, buffering capacity increased much higher. In wear trials it was confirmed that the buffering index obtained by the apparatus was in good agreement with the subjective sensation of wetness.