A recombinant T-cell engaging bispecific monoclonal antibody (BiTE) directed against human prostate specific membrane antigen (PSMA) and the CD3 epsilon subunit of the T cell receptor complex, with potential immunostimulating and antineoplastic activities. Anti-PSMA/CD3 BiTE monoclonal antibody MT112 possesses two antigen-recognition sites, one for PSMA, and one for the CD3 complex, a group of T cell surface glycoproteins that complex with the T cell receptor (TCR). This bispecific monoclonal antibody brings PSMA-expressing tumor cells and cytotoxic T lymphocytes (CTLs) together, which may result in the CTL-mediated cell death of PSMA-expressing cells. PSMA, a tumor associated antigen, is overexpressed on the surface of metastatic and hormone-refractory prostate cancer cells.