This invention relates to monovalent and multivalent, monospecific antibodies and to monovalent and multivalent, multispecific antibodies. One embodiment of these antibodies has one or more identical binding sites where each binding site binds with a target antigen or an epitope on a target antigen. Another embodiment of these antibodies has two or more binding sites where these binding sites have affinity towards different epitopes on a target antigen or different target antigens, or have affinity towards a target antigen and a hapten. The present invention further relates to recombinant vectors useful for the expression of these functional antibodies in a host. More specifically, the present invention relates to the tumor-associated antibody designated PAM4. The invention further relates to chimeric PAM4 antibodies, and the use of such antibodies in diagnosis and therapy.