The intermolecular potential surfaces for the Van der Waals complexes He-CH 4 and Ne-CH 4 are studied by ab initio theory using complete fourth-order M ller-Plesset perturbation theory (MP4) with an efficient basis set containing bond functions. For He-CH 4 , the global minimum occurs at R = 3.4 9, θ = 180°, φ = 0° (in a Jacobi coordinate system) with a minimum energy D e = -26.2 cm - 1 . For Ne-CH 4 , the global minimum occurs at R = 3.5 9, θ = 180°, φ = 0° with a minimum energy D e = -59.0 cm - 1 . Two saddle points were found for each of the systems. The potential energy surfaces are compared with the semiempirical surfaces and recent ab initio results on the same systems.