A practical manual presenting step-by-step protocols designed to help biologists develop an immunoassay in any common format for any suitable analyte. Describes methods for raising and choosing polyclonal and monoclonal antibodies, immunogen preparation and characterization, sourcing standards, the synthesis and characterization of radioactive, enzymatic, fluorescent, and ligand labels, the preparation of a wide variety of solid-phase reagents, assay optimization, validation of quantitative and qualitative assays, curve fitting and data processing, and quality assurance procedures for small- and large-scale users.