A radioimmunoconjugate, which consists of a monoclonal antibody against the cell-surface antigen CD37 covalently linked, via the bifunctional, macrocyclic chelating agent tetra-azacyclododecanetetra-acetic acid (DOTA), to the beta-emitting radioisotope lutetium Lu 177, with potential antineoplastic activity. The antibody moiety of lutetium Lu 177 DOTA-tetulomab binds to CD37 on tumor B-cells. Upon internalization, the radioisotope moiety delivers a cytotoxic dose of beta radiation to CD37-expressing tumor cells. CD37, a transmembrane glycoprotein, is overexpressed in B-cell malignancies.