The present invention discloses bispecific antibodies comprising two antibody variable domains on a single polypeptide chain, wherein a first portion of the bispecific antibody is capable of recruiting the activity of a human immune effector cell by specifically binding to an effector antigen on the human immune effector cell, the first portion consisting of one antibody variable domain, and a second portion of the bispecific antibody specifically binding to a target antigen other than the effector antigen, the target antigen on a target cell other than the human immune effector cell, the second portion comprising one antibody variable domain.