Donor lymphocyte infusions, by virtue of a graft-versus-tumor effect, have been shown to induce remissions in leukemia that recurs after allogeneic bone marrow transplantation. Similar effects have been postulated to contribute to the decreased recurrence rate observed after allogeneic transplantation in non-Hodgkin's lymphoma. This lower recurrence rate may be due to a variety of other mechanisms. We aimed to evaluate the role of graft-versus-lymphoma effects in patients in whom lymphomas recur after allogeneic transplantation. At the time of recurrence, immunosuppressive therapy was withheld. Patients with non-responding disease received an infusion of donor lymphocytes. Patients were observed for response and graft-versus-host disease. Disease in four of nine patients responded to withdrawal of immunosuppressive therapy. A minor response was observed in one of three recipients of donor lymphocyte infusions. Responses were observed among two patients with follicular lymphoma, one with large cell lymphoma and one with lymphoblastic lymphoma. A minor response was observed in a patient with prolymphocytic leukemia/lymphoma. We conclude that withdrawal of immunosuppressive therapy and donor lymphocyte infusion can induce durable remissions in patients with recurrent lymphoma after allogeneic transplantation.