The humanized monoclonal antibody huPAM4, directed against the pancreatic cancer antigen MUC-1 and radiolabled with the gamma-emitting radioisotope indium I 111, with radioisotopic and antibody activities. Upon administration, indium In 111 monoclonal antibody huPAM4 may bind to MUC-1-positive tumor cells, allowing radioimmunolocalization with gamma scintigraphy. Overexpressed by many tumor cell types, MUC-1 antigen, a mammary-type apomucin, is a high-molecular-weight transmembrane glycoprotein.