Various amounts of a bacterially produced lipid-tagged single-chain antibody were incorporated into phospholipid monolayers preformed at the air-water interface. The mixed layers were transferred onto octadecyl mercaptan-treated gold films, and the binding of hapten, which was used as antigen, was determined by surface plasmon resonance. Incorporation of the single-chain antibody, transfer of the layer onto solid slides, amount of nonspecific adsorption, and thus the amount of specific binding depended on the composition of the lipid matrix. Studies by atomic force microscopy revealed that the film consisted of antibody-enriched lipid domains and that the films were not stable when stored long times in aqueous solution.