pIn this volume we will cover technologies and associated methodologies that allow identification, characterization and application of therapeutic peptides.p pp pThe section covering identification will cover areas such as display on the surface of filamentous or lytic phage, substrate phage display, ribosome display and the use of peptide library pools. p pp pOften the output from library selection is not a peptide but the sequence of a peptide. We will therefore discuss approaches to produce peptide ligands both synthetically and through recombinant techniques. This section will also include a discussion of how peptides may be produced such that their serum residence time can be extended to allow weekly dosing such as fusions to other larger proteins or through modification with PEG.p pp pThe next section covers biophysical tools for characterization of peptide interactions with proteins. These include fluorescence polarization, equilibrium dialysis, radioligand binding assays, regul