The surface diffusivity was determined from analysis of pressure response versus time, using a previously developed linear mathematical model. To apply the linear theory over the non-linear range of the adsorption isotherm, a differential increment method was applied to the system, which was initially equilibrated with some pre-determined loading. By conducting the experiments for differing initial loadings, the surface diffusivity could be extracted as a function of loading. Propane, n-butane, n-hexane, benzene, and ethanol were used as diffusing adsorbate on a commercial activated carbon. It was found that the surface diffusivity of these strongly adsorbing vapours increased rapidly with loading, and the surface diffusion flux contributed significantly to the total flux and could not be ignored. The surface diffusivity increased with temperature according to the Arrhenius law, and for the paraffins tested it decreased with the molecular weight of the adsorbate. Surface Diffusion of Strong Adsorbing Vapours on Porous Carbon. Prasetyo, I., Do, H.D., Do, D.D.: Chemical Engineering Science, 2002, 57[1], 133-41