Natural soil deposits are generally anisotropic as well as heterogeneous. In order to provide a guideline for estimating a reasonable strength parameter applicable to such complex soils, plane strain tests on uniform-anisotropic, uniform-pseudoisotropic, layered-anisotropic, and layered-pseudoisotropic samples have been performed. Anisotropic strength response, caused by the anisotropic distribution of contact normals, should be expected even in a uniform mass of spheres. It is always necessary to assume that sand is generally anisotropic. Tests on samples prepared by the plunging-tapping method are advisable for obtaining a reasonable estimate of the mean strength for anisotropic sands.