A nucleic acid comprising a base sequence which codes for a CEA family member peptide sequence or nucleic acids having a base sequence hybridizable therewith, replicable recombinant cloning vehicles having an insert comprising such nucleic acid, cells transfected, infected or injected with such cloning vehicles, polypeptides expressed by such cells, synthetic peptides derived from the coding sequence of CEA family member nucleic acids, antibody preparations specific for such polypeptides, immunoassays for detecting CEA family members using such antibody preparations and nucleic acid hybridization methods for detecting CEA family member nucleic acid sequences using a nucleic acid probe comprising the above described nucleic acid.