Methods, compositions and kits comprising dimeric antibodies for the treatment of neoplastic, autoimmune or other disorders are provided. The dimeric antibodies of the instant invention may comprise two antibody molecules (H.sub.4L.sub.4) having the same antigen binding specificity (homodimers) or, alternatively, may comprise two different antibody molecules having binding specificity for two distinct antigens (heterodimers). In preferred embodiments the antibody molecules comprising the dimers are non-covalently associated.