A mouse/human-chimeric bispecific antibody, designated CBA-CEACD3, with dual specificities for carcinoembryonic antigen (CEA) and CD3, was generated by chemical cross-linking of a chimeric antibody specific for CEA to another chimeric antibody against CD3. Flow cytometric analysis showed that CBA-CEACD3 can bind specifically to cells expressing CEA and to normal human peripheral blood mononuclear cells (HPBMCs) bearing CD3, respectively. Furthermore, a cell to cell adhesion analysis by a colorimetric assay using the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) demonstrated that CBA-CEACD3 is able to bind CEA-producing cells to CD3-expressing cells, suggesting that both arms of CBA-CEACD3 are simultaneously working and can retarget T-cells to the tumor. In an additional colorimetric assay using MTT, this antibody was shown to effectively mediate CEA-expressing tumor cell killing by freshly isolated HPBMCs. Together these results demonstrate that this chimeric bispecific antibody may serve as a potentially useful immunotherapeutic reagent for human CEA-producing cancers.