Discloses an immunoconjugate comprising an isolated anti-Epidermal Growth Factor Receptor (EGFR) antibody attached to a cytotoxic agent, wherein the anti-EGFR antibody is an IgG1 isotype, comprises a heavy chain comprising a heavy chain variable region comprising the amino acid sequence set forth in SEQ ID NO: 164, and comprises a kappa light chain comprising a light chain variable region comprising the amino acid sequence set forth in SEQ ID NO: 166, wherein the antibody is expressed in a mammalian cell, wherein the sequences are as defined in the complete specification.