Some of the most dramatic advances in the treatment of cancer have used the immune system in combination with conventional or transplantation chemotherapy. Adoptive immunotherapy has been used for relapses after allogeneic bone marrow transplantation, and it has been particularly effective for chronic myeloid leukemia. Adoptive immunotherapy also has been used for Epstein-Barr virus-related lymphomas developing after allogeneic marrow transplantations. Cellular therapy, including the infusion of tumor-reactive immune cells, has been used to mediate response of established solid tumors. This has been used for therapeutic benefit for renal cell carcinoma, melanoma, lung cancer, and breast cancer. Current research is focusing on reducing the toxicity of these approaches as well as further defining the appropriate target tissue.