The surface impedance for grazing incidence over a 1° dielectric wedge on a perfect conductor was investigated experimentally at 4.75 GHz. The results were compared with simple two-layer parallel stratified theory, and the geometrical-optics theory given by Schlak and Wait for propagation over a wedge region composed of two media. The experiment was designed to investigate the limitations of these theories.The directive nature of the surface impedance is discussed, and it is concluded that the difference in the surface impedance for the two directions of propagation can be attributed entirely to scattering. If the surface is well suited to support a surface wave and scattering is not the dominant feature, simple parallel two-layer theory seems to best describe the surface impedance. On the other hand, if the surface supports a surface wave poorly and there is significant scattering, geometrical-optics theory works best.A recent full wave solution given by Bahar was used to explain some of the limitations of the geometrical-optics theory, and the conclusions drawn from the experimental data concur with his analysis.