The adsorption isotherms and kinetics of gaseous methane onto highly porous activated carbon (Maxsorb-III) at temperatures ranging from 278 to 333 K and at different equilibrium pressures between 0.1 and 2.0 MPa have been experimentally measured by the desorption method unlike volumetric or thermo-gravimetric apparatus. The thermophysical properties such as skeletal density, BET surface area, pore size, pore volume and the total porosity of Maxsorb-III have been determined. The Dubinin-Astakhov(DA) and Langmuir isotherm models are found to fit well all of the experimental data within the experimental errors. The experimental isotherms and the computed isosteric heat of adsorption are compared with the measurements of similar specimens of activated carbon of other researchers, and found to be consistent. The present isotherm and isosteric heat data are useful for designing environmentally benign adsorption cooling and storage systems.