A monoclonal antibody directed against transforming growth factor-beta receptor type II (TGF-beta RII) with potential antineoplastic activity. Anti-TGF-beta RII monoclonal antibody IMC-TR1 specifically targets and binds to TGF-beta R11, thereby preventing the activation of TGF-beta RII-mediated signaling pathways. TGF-beta RII is mutated in a number of cancer cell types and is involved in cancer cell proliferation and tumor progression.