A series of experiments is performed on the combined heat and water vapor transfer through fabric at simulated high altitudes. A considerable water vapor concentration difference is imposed between the water vapor source and the environment, so that condensation takes place in the specimen. A new analytical expression for the rate of condensation in textile materials is derived by considering the combined heat and mass transfer between the specimen and the environment. Although the amount of condensation in textiles can not be correlated well by primitive parameters such as temperature or water vapor concentration differences, good agreement can be obtained between the condensa tion mass flux measured experimentally and that calculated by means of the derived expression.