The dependence of the shadowing function on grazing angle was optically measured on three rough surfaces which are identical except for the rms reliefs (and slopes) which had been scaled in the ratios 1 : 2 : 4. Both one‐ and two‐dimensional shadowing measurements were made. The one‐dimensional measurements are in good agreement with the one‐dimensional theory of shadowing developed by R. J. Wagner. In addition, the one‐ and two‐dimensional shadowing measurements are in excellent agreement with one another as would be expected for nearly isotropic surfaces.