A recombinant humanized monoclonal antibody directed against human CD20 with potential antineoplastic activity. Upon intravenous administration, anti-CD20 monoclonal antibody B001 specifically binds to CD20 on the surfaces of B-cells. Although the exact mechanisms through which B001 exert its effects have not been elucidated, B001 may induce a B-cell directed cell-mediated immune response against CD20-expressing B-cells and/or prevent CD20-medaited signaling. This induces tumor cell apoptosis and inhibits proliferation. CD20 is a non-glycosylated cell surface phosphoprotein which is exclusively expressed on B-cells during most stages of B-cell development and which is often overexpressed in B-cell malignancies.