Recent technological advances, together with the discovery of the important role many growth factors play in modulating cell proliferation and differentiation, have led to the development of novel therapeutic agents for the treatment of cancer. In particular, advances in hybridoma technology and molecular engineering have permitted the development of humanized or chimeric monoclonal antibodies capable of interfering with growth factor signaling pathways. One promising target of interest is the epidermal growth factor receptor (EGFr), which is activated by the ligands EGF and TGF-alpha. This ligand receptor interaction plays a crucial role in the growth and survival of many human cancers. A chimeric (human/mouse) monoclonal antibody p6tuximab (IMC-C225) targets the EGFr and has potential clinical value as an anticancer agent.