Microporous polypropylene membranes were used to transfer oxygen to water where the gas phase was pure oxygen saturated with water vapor The experiments were maintained at a constant temperature of 37 degrees C. Flow channel length, channel thickness, liquid velocity and operating pressure were changed so as to investigate their effects on mass transfer performances. A model for non-wetted pores was derived, by neglecting the gas phase film and pore resistances, and numerically solved in order to find the concentration distribution and the local average concentration in the liquid phase. This model was further developed for wetted ports in order to reflect the true operating conditions. Wetting ratio was found by the matching of model predicted concentration profiles with the experimental results. Oxygen flux and liquid side film coefficient were also calculated by using experimental data. All of the results of this work were in agreement with the literature. (C) 2000 Elsevier Science B.V. All rights reserved.