Hybridoma technology has the potential for producing an unlimited quantity of monospecific antibodies that are ideal serological reagents for taxonomic, diagnostic, structural, and biochemical analyses of plant viruses. One of the most misleading concepts which have grown up around monoclonal antibodies (mAb) technology is that there is no need to purify the antigen used for immunization. The screening procedures used to identify antibody-secreting hybridomas are the important step for the production of mAbs. If mAbs will be used in Western blotting analyses or in immunoelectron microscopic analyses, those mAb-secreting hybridomas need to be screened by Western blotting analyses or by immunoelectron microscopic analyses, respectively. Several immunological assays are used to determine overlapping epitopes of mAbs in laboratory. Microprecipitin tests were performed by mixing antigens with antibodies in phosphate-buffered saline. Many virus-specific mAbs did not precipitate viruses or coat proteins in microprecipitin or immunodiffusion tests.