An improved equivalent network approach in which all of the discrete and the continuous parts of the spectrum are taken into account is described for the guided wave problems in the dielectric waveguide placed on a ground plane. A network representation is derived individually for each of the constituents of the cross section of the waveguide--transmission lines for the uniform regions and lumped equivalent networks for the geometrical discontinuities, namely the sides of the waveguide. These lumped networks are evaluated explicitely by using the Rayleigh-Ritz variational technique. The present equivalent network approach can give more accurate results for the various dielectric waveguides over a wide range of frequencies than the earlier equivalent network approach in which only the coupling between the same order discrete modes at the sides of the waveguide is taken into account.