Abstract: This invention concerns a family of chimeric antibodies with high affinities to a high molecular weight, tumor-associated sialylated glycoprotein antigen (TAG-72) of human origin. These antibodies have (1) high affinity animal VH and VL sequences which mediate TAG-72 binding and (2) human CH and CL regions. They are thought to produce significantly fewer side-effects when administered to human patients by virtue of their human CH and CL antibody domains. The nucleotide and amino acid sequences of VH&agr;TAG VH, CC46 VH, CC49VH, CC83 VH, and CC92 VH, and CC49VL, CC83 VL, and CC92 VL idiotype sequences are disclosed, as well as in vivo methods of treatment and diagnostic assay using these chimeric antibodies.