Two high-frequency methods are used to compute the scattered fields from both square and triangular trihedral corner reflectors. Scattering from a trihedral corner reflector is dominated by single, double, and triple reflections. Both methods use Physical Optics (PO) to calculate the single reflected fields. For the evaluation of the double and triple reflected fields, the first method uses Geometrical Optics (GO) for the initial reflections and PO only for the last reflection. On the other hand, the second method uses PO for the last two consecutive reflections. In addition to the reflected fields, the two methods use the Method of Equivalent Currents (MEC) to calculate the single diffracted fields from all the exterior edges. Higher-order terms, such as multiple diffractions, reflection-diffractions and diffraction-reflections, are not included in the analysis. The backscattered fields are computed for incident angles along both elevation and conical paths. The predicted results are compared with measurements and Finite Difference Time Domain (FDTD) data.