High-pressure excess adsorption equilibria of methane and carbon dioxide on five microporous activated carbons were measured. Adsorption isotherms were obtained at temperatures ranging from (273 to 333) K and at pressures ranging from (0.5 to 6000) kPa using a static volumetric apparatus. The experimental data were analyzed using the Toth model and the Dubinin-Astakhov model. The isosteric enthalpies of adsorption and the limiting heat of adsorption for both adsorbates on all activated carbons were calculated using the Clausius-Clapeyron equations and the van't Hoff equations, respectively.