This work examines the gas transport and sorption properties of a commercial acrylonitrile-butadiene-styrene (ABS) copolymer (Lustran(R)246), containing 60% styrene, 27% acrylonitrile and 13% butadiene. Permeability, diffusion and sorption coefficients of CO2, CH4, N-2 and O-2 in ABS membrane were determined at temperatures from 20 to 50degreesC and pressures in the 2-10 x 10(5) Pa range. The coefficients correspond to the van't Hoff and Arrhenius relationships. In order to analyze the effect of plasticization, permeation properties were also determined at a feed pressure of 2 x 10(6) Pa with a 50% CO2/CH4 mixture. Interesting 02 permeability values and O-2/N-2 separation factors in the whole range of temperature studied were obtained.The results presented and discussed in this paper suggest that the ABS copolymer can be used as membrane material for the separation of O-2/N-2 at moderate temperature (20-50degreesC), as far as it exhibits a balance of adequate thermal, mechanical and gas separation properties. (C) 2003 Elsevier B.V. All rights reserved.