The invention relates to murine monoclonal antibodies (MAbs), A, B, C and D, which are directed against tumor-associated antigens. The nearly complete nucleotide sequences of the V genes of these MAbs are described, so that the relevant variable domains can be put together to give chimeric MAbs, or “humanized” MAbs are obtained by inserting the hypervariable regions (complementarity determining regions=CDR) into a human MAb framework. Antibody constructs of this type can be employed in human therapy and in vivo diagnosis without the disadvantages observed with murine MAbs.