An anti-carcinoembryonic antigen (CEA)/anti-CD3 bispecific monoclonal antibody with potential antineoplastic activity. Anti-CEA/CD3 monoclonal antibody RO6958688 contains two antigen-recognition sites: one for human CD3, a T-cell surface antigen, and one for human CEA, a tumor-associated antigen that is specifically expressed on certain tumor cells. Upon intravenous administration, RO6958688 binds to both T-cells and CEA-expressing tumor cells, which cross-links the T-cells with the tumor cells. This may result in a potent cytotoxic T-lymphocyte (CTL) response against CEA-expressing tumor cells. CEA is overexpressed in many cancer cell types.