Epitope mapping is the process of experimentally identifying the binding site, or "epitope", of an antibody on its target antigen (usually, on a protein). Identification and characterization of antibody binding sites aid in the discovery and development of new therapeutics, vaccines, and diagnostics. Epitope characterization can also help elucidate the mechanism of binding for an antibody and can strengthen intellectual property (patent) protection. Experimental epitope mapping data can be incorporated into robust algorithms to facilitate in silico prediction of B-cell epitopes based on sequence and/or structural data. Epitopes are generally divided into two classes: linear and conformational. Linear epitopes are formed by a continuous sequence of amino acids in a protein. Conformational epitopes are composed of amino acids that are discontinuous in the protein sequence but brought together upon three-dimensional protein folding. B-cell epitope mapping studies suggest that most interactions between antigens and antibodies, particularly autoantibodies and protective antibodies (e.g., in vaccines), rely on binding to conformational epitopes. By providing information on mechanism of action, epitope mapping is a critical component in therapeutic monoclonal antibody (mAb) development. Many therapeutic mAbs target conformational epitopes that are only present when the protein is in its native (properly folded) state, which can make epitope mapping challenging.