The present invention relates to antibodies which are directed to the EGF receptor (HER1) to be administered especially to humans and in particular for therapeutic use in tumors. The antibodies are modified whereby the modification results in a reduced propensity for the antibody to elicit an immune response upon administration to the human subject. The invention in particular relates to the modification of anti-EGFR antibody 425 in its different forms and fragments thereof to result in Mab 425 variants that are substantially non-immunogenic or less immunogenic than any non-modified counterpart when used in vivo.