A novel analysis to compute the admittance characteristics of the slots cut in the narrow wall of a rectangular waveguide (also called edge slot) is presented. The slot aperture field is expanded in terms of entire domain sinusoidal basis functions and is solved using Galerkin's method. The computed results have been compared with the measured data published in the previous literature to validate the present analysis. The validity of representing the edge slot as a shunt element is examined and an alternate way of representing the edge slot is suggested as being more accurate. © 1998 John Wiley & Sons, Inc.