Abstract: The present invention is directed to a combination therapy for the treatment of cancer and pathogen-associated diseases, that comprises the administration of: (I) a molecule (e.g., a diabody, an scFv, an antibody, a TandAb, etc.) capable of binding PD-I or a natural ligand of PD-I, and (2) a molecule (e.g., a diabody, a BiTe, a bispecific antibody, a CAR, etc.) capable of mediating the redirected killing of a target cell (e.g., a cancer cell or a pathogeninfected cell, etc.) expressing a Disease Antigen. The invention particularly concerns the embodiment in which the molecule capable of mediating the redirected killing of the target cell is a bispecific binding molecule that comprises a first epitope-binding site capable of immuno specifically binding an epitope of a cell surface molecule of an effector cell and a second epitope-binding site that is capable of immuno specifically binding an epitope of such target cells.