Abstract: This invention relates generally to the field of immunology, in particular that of antibodies and antibody productions. More specifically, this invention relates to bispecific antibodies, the hybrid hybridomas which produce them, the parent hybridomas, the production and selection of the hybridomas and hybrid hybridomas, and the purification of the bispecific antibodies. Specific examples relate to bispecific monoclonal antibodies which recognize both the human multi-drug resistance antigen, P-glycoprotein and human Fc.gamma. receptor III (hFc.gamma.RIII. These bispecific antibodies are useful in killing cancer cells.