The long-range order of spherical block copolymer films is greatly improved if the underlying surface has been etched to form wells and mesas. Epitaxial growth of polystyrene/poly (2-vinylpyridine) block copolymers on po SiO2 with structures 1-10 mum wide yields single-crystal-like structures on top of the mesas (see Figure), and in the wells, provided the height of the mesas exceeds one layer of copolymer spheres (27 nm). (See also inside front cover.).