Abstract-The Least-Squares Boundary Residual Method is employed in the present paper to develop a computer model of the symmetrical six-port waveguide junction. The analytical formulation is difficult because of the insertion of a metallic post together with a dielectric sleeve into the over-sized cavity of the junction. Computational and experimental tests confirm that the resultant model is able to compute the scattering parameters of such a structurally-complicated component with numerical accuracies of ±0.001 and ±0.1 • for magnitude and phase respectively.