The surface structure and cast film formation process of a ZnS-nanocrystal-modified M13 bacteriophage (ZnS-M13) were investigated. A ZnS-M13 film oriented under the influence of a capillary force was obtained on both single-crystal and poly-crystalline substrates. The film formation process was investigated with atomic force microscopy and scanning electron microscopy. The surface images showed that the degree of orientation of the molecular long axes greatly depended on the direction of force and the concentration of aqueous solutions. Controlling the aqueous solution concentration yielded a highly oriented ZnS-M13 film on an indium tin oxide plate. The ability to control the orientation of virus-based films may lead to new types of hybrid materials in which the components are organized on several length scales. (C) 2004 Wiley Periodicals, Inc.