Peptide antigens and their antibodies have been widely exploited for the measurement, location, and purification of oligopeptides such as peptide hormones. Recently, the use of peptides to mimic substructures of proteins has led to major expansion in the application of anti-peptide antibodies. These have been especially important in identifying the characterizing proteins which are only known by their primary structure derived from a DNA sequence. Another area of recent expansion is the use of defined peptided antigens to identify and map antibodies and T-cell receptors. This book provides information and detailed protocols for the main techniques for exploitation of peptide antigens and anti-peptide antibodies, and will interest research workers in many fields.