Recently, phage display techniques have been applied to various biological aspects. Phage can be exploited to display peptides, protein domains and proteins on its surface. Especially peptide phage display is now well established as a tool for the search for peptides binding to antibodies, enzymes, receptors, lectins, nucleic acids or other target molecules and in studying the substrate specificity of enzymes. It has great potential for application in the areas of drug discovery, vaccine development and other pharmaceutical development.