Since the initial description of techniques to immortalize anti­ body-producing B-lymphocytes by fusion with tissue culture-adapted myeloma cells, methods have been developed to produce monoclonal antibodies of defined specificity in multiple animal species. Stable hybrids can be readily produced in mice using a number of myeloma and hybridoma cell lines. To obviate the problem of identifying fusion partners in other animal species, xenohybrids have been produced using B-lymphocytes from the relevant species and mouse myeloma cells. The use of xenohybrids has minimized the problem of obtain­ ing stable antibody-producing hybrids in all species examined thus far. Although alternative techniques are being developed to produce monoclonal antibodies by molecular methods, hybridoma technol­ ogy will remain the technology of choice for producing monoclonal antibodies for a variety of applications in research and industry. The objective of Monoclonal Antibody Protocols is to provide investigators with a set of methods for producing and using mono­ clonal antibodies in biomedical, agricultural, and biological sciences. The book is not intended to provide methodology for all possible applications, but rather a series of methods presented in an easy-- follow format that can be used by new and established investiga­ tors, graduate and postgraduate fellows, and technical staff.