A new approach is proposed for dielectric multistep discontinuity in guiding structures which combines edge-element analysis with the mode-matching method and multimode network theory. It is demonstrated that the approach has the generality of the edge-element analysis and the simplicity of the multimode network method, while retaining the high accuracy of the mode-matching method. The calculations for different multistep discontinuities verify the effectiveness and suitability of the approach for analysis of three-dimensional (3-D) lossy dielectric discontinuity problem.