A radioimmunoconjugate consisting of the murine IgG1 kappa monoclonal antibody capromab (7E11-C5.3), conjugated to the linker-chelator glycyl-tyrosyl-(N,-diethylenetriaminepentaacetic acid)-lysine hydrochloride (GYK-DTPA-HCl) and labeled with radioisotope indium In 111, with ligand-binding and gamma-emitting activities. Upon intravenous administration, indium In 111-capromab pendetide binds to a cytoplasmic epitope of human prostate specific membrane antigen (PSMA) expressed on prostate tumor cell surfaces via its capromab moiety and, upon internalization, allows radioimmunolocalization with gamma scintigraphy. PSMA is a cell surface glycoprotein abundantly expressed by prostate epithelium and is typically overexpressed by prostate cancer cells.