Graft-versus-tumor effects can be achieved after allogeneic bone marrow transplantation in patients with malignancies of the kidney or hematopoietic system but are often accompanied by severe graft-versus-host-disease (GVHD). We sought to maximize graft-versus-tumor while minimizing GVHD using tumor-specific allogeneic effector T cells rather than open-repertoire T cells. We transferred allogeneic CD8(+) pmel-1 or CD4(+) TRP-1 T cells specific for the melanoma-associated antigens, glycoprotein 100 (gp100) and tyrosinase-related protein-1 (TRP-1), respectively, into B16-melanoma-bearing mice. Mice receiving a preparative regimen of nonmyeloablating (5 Gy) total body irradiation experienced the rapid rejection of tumor-specific allogeneic lymphocytes with no impact on tumor growth. However, when mice were given more intense total body irradiation conditioning regimens combined with autologous bone marrow transplantation, adoptively transferred allogeneic tumor-specific T lymphocytes persisted at detectable levels for several weeks and mediated significant regression of large, vascularized tumors. We found that the risk of GVHD was low when tumor-specific T cells were transferred and significant toxicity was observed only when substantial numbers of open repertoire allogeneic naive T cells were mixed with the tumor-specific lymphocytes. Taken together, these data indicate that the use of tumor-specific allogeneic CD8(+) T cells or CD4(+) can result in significant antitumor effects in the absence of measurable GVHD.