The purpose of this paper is to clarify the mechanism of air permeability of clothing materials relating with thermal comfortability of the clothing and thereby to obtain some findings for the fabric performance design. Air resistances, R (kPa? sec/m), were measured for 9 groups for fabrics of different end-uses using the air permeability tester which had recently developed by S. Kawabata. As the result of measurement of R under the constant air flow rate of 0. 04 (m³/ (m²·sec)), the ranges of R for each group were confirmed. We found the positive correlation between R and the weight and also between R and the apparent density in these fabrics, but we could not find clear correlation between R and thickness in them.