The intermolecular interaction energies of 132 geometrical configurations of methane dimers were calculated by an MP3/6-311 G(3d,3p)-level ab initio method. Nonbonding interaction parameters were fitted using three models (isotropic hydrogen, anisotropic hydrogen, and anisotropic hydrogen with electrostatic interaction) to reproduce the ab initio results. The incorporation of the anisotropy of the nonbonding interaction of hydrogen decreased the RMS error drastically. On the other hand, the incorporation of the electrostatic interaction improved the fitting little. The density, heat of evaporation, and self-diffusion coefficient of liquid methane were calculated by molecular dynamics simulations with the second- and the third-model parameters. The calculated density of 0.38 g cm(-3), the heat of evaporation of 1.7 kcal/mol, and the self-diffusion coefficient of 6.0 x 10(-9) m(2)/s from the second-model parameters and 0.38, 1.7, and 6.5 from the third-model parameters were close to the experimental values of 0.42, 2.0, and 5.4, respectively.