The potential energy function of methane has been determined via the inversion of reduced viscosity collision integrals at zero pressure. A comparison of the potential with the previously determined potentials is included. The viscosity, thermal conductivity, and self-diffusion coefficient of methane at different temperatures and pressures have been calculated and compared with experiment. The interaction potential of methane from the inversion method has been fitted to obtain an analytical potential form. (C) 2003 Elsevier B.V. All rights reserved.