Removal of trace H2S from gas streams containing high concentration of CO2 was carried out in a polyvinylidene fluoride porous asymmetric hollow fibre membrane module, using an aqueous solution containing 2 M sodium carbonate as absorption medium. Effects of gas/liquid flow ratio, CO2 Concentration and operating pressures on the extent of H2S removal, H2S selectivity and overall mass transfer coefficients were investigated. The selectivity for H2S was about one order of magnitude higher than that in conventional-packed towers. Using feed gas mixtures containing 1000 ppm H2S with CO2 concentrations ranging from 5-23 vol.%, the H2S removal efficiency of nearly 100% was attained with less than 5 Vol-% of CO2 permeated and absorbed. Experimental results indicate that the membrane module used was very efficient in the selective removal of trace H2S to ultra-low concentration even at high gas/liquid flow ratio. (C) 2003 Elsevier B.V. All rights reserved.