The invention relates to murine/human chimeric monoclonal antibodies with high specificity to and affinity for human carcinoembryonic antigen (CEA), derivatives thereof, processes for the preparation of these antibodies and their derivatives, DNAs coding for heavy and light chains of these antibodies, processes for the preparation of said DNAs, mammalian cell lines that produce and secrete the antibodies and processes for the preparation of said cell lines. The chimeric antibodies and their derivatives are used for clinical purposes in vitro and in vivo, especially for the diagnosis of cancer, for localization and in vivo imaging of tumors, for therapy, e.g. site-directed delivery of cytotoxins, and similar purposes. The invention also concerns test kits and pharmaceutical compositions containing said chimeric monoclonal antibodies and/or derivatives thereof.