Determination of the boundary conditions of a surface from the remote field measurements is an important and interesting topic in the inverse scattering theory. As an example of such problems a method is developed for the reconstruction of the surface impedance of a planar boundary beyond a layered structure. The surface impedance is recovered from the boundary condition itself, which requires that the field distribution and its derivative on the surface be known. The measured data are analytically continued to the boundary to obtain the required field expressions. The computed results obtained for some illustrative examples through the theory established here have very good agreement with the exact values, which shows that the method is accurate and effective. ¿ 2001 American Geophysical Union