The chimeric anti-CD20 antibody rituxamab, as well as radiolabeled anti-CD20 monoclonal antibodies, have demonstrated significant activity against B-cell non-Hodgkin's lymphoma. Idiotype vaccination in remission may prevent relapse in follicular non-Hodgkin's lymphoma. The campath-1H antibody has activity in chronic lymphocytic leukemia, and additional unconjugated, radiolabeled, and drug-conjugated monoclonal antibodies (anti-CD45 and anti-CD33) have shown activity in acute myeloid leukemia. Adoptive cellular therapy is active against posttransplantation relapse and lymphoproliferative disorders in most patients, and complications of graft-versus-host disease may be controlled by suicide gene transfection of the donor lymphocytes.