Modification of the gas transport properties of rolltruded isotactic poly(propylene) films have been studied. Changes in the amorphous solubility, diffusivity, and the activation energies of CO2, N-2, and CH4 in iPP rolltruded at 150 degrees C for draw ratios to ca. 20 are recorded. At this processing temperature variations in the transport coefficients have been found to be weakly dependent upon draw ratio and do not suffer the dramatic reductions often reported in uniaxially drawn polymers. In general, the morphological differences between uniaxially drawn and rolltruded films are subtle and are responsible for the significant difference in the measured transport properties.