We present the clinical results of allogeneic bone marrow transplantation (BMT) with T-cell-depleted grafts from HLA-matched sibling donors in patients with poor-risk relapsed low-grade non-Hodgkin's lymphoma (NHL). Poor risk was defined as relapse within 12 months after or progression during prior treatment. The conditioning regimen consisted of cyclophosphamide and total-body irradiation with or without additional idarubicin. Donor marrow was depleted of T lymphocytes using counterflow centrifugation. Post-BMT prophylaxis of graft-versus-host disease (GvHD) consisted of cyclosporine A. 15 patients with a median age of 47 years (range 30-57) were transplanted. All patients engrafted. After a median follow-up of 36 months (range 9-78), 10 patients were alive and in complete remission (CR). Two of them had relapsed after BMT but re-entered CR following infusions of leucocytes from the original bone marrow donor. Five patients died; causes of death were cardiomyopathy (n = 1), chronic GvHD (n = 1) and infection during chronic GvHD (n = 3). We conclude that allogeneic T-cell-depleted bone marrow transplantation is an efficacious treatment for patients with poor-risk relapsed low-grade NHL. Infusions of donor leucocytes reinduced CR in the two patients with relapse after BMT.