A procedure for the orientation of antibody fragments at the gas-water interface is described and preliminary results are presented. The method exploits the presence of the reactive sulfhydryl group of a reduced antibody fragment which can react with a floating monolayer. Surface pressure measurements show a strong interaction between the reduced fragments and the monolayer. Deposited films are characterised by a fluorescent immunoassay and ellipsometry and the results indicate that the antibody fragments are oriented with a high packaging density.