The present disclosure relates to a bispecific single chain antibody which has a first binding domain specifically binding to human CD3, and a second binding domain specifically binding to human CEA, where the second binding domain comprises at least a part of the CDR-H3 or the complete CDR-H3 of murine monoclonal antibody A5B7, a pharmaceutical composition comprising the bispecific single chain antibody, and methods for the treatment of an epithelial tumor in a human with the pharmaceutical compositions containing the bispecific single chain antibody. Furthermore, processes for the production of the pharmaceutical compositions as well as medical/pharmaceutical uses for the specific bispecific single chain antibody molecules bearing specificities for the human CD3 antigen and the human CEA antigen are disclosed.