Donor leukocyte transfusions for treatment of recurrent chronic myelogenous leukemia in marrow transplant patients. Three patients with hematologic relapse after bone marrow transplantation for chronic myelogenous leukemia were treated with interferon alpha and transfusion of viable donor buffy coat. All had complete hematologic and cytogenetic remission, which persisted 32 to 91 weeks after treatment. In two patients graft-versus-host disease developed and was treated by immunosuppression. These results are an example of adoptive immunotherapy without cytoreductive chemotherapy or radiotherapy in human chimeras. 