Between October 1983 and October 1985, 12 allogeneic bone marrow transplantations from HLA-identical siblings were performed for treatment of malignant disease (11 haemopoietic malignancies) or severe aplastic anaemia (1 case). All patients showed prompt and complete engraftment of donor cells on average around day 17 after transplantation. 10 patients are alive and well 50-760 days after transplantation, without any signs of recurrence and partly without immunosuppressive therapy. Two patients died, one due to relapse of the leukaemia, and one as a result of CMV interstitial pneumonia. Graft versus host disease was seen in 6 of the 12 patients. Additional immunosuppressive therapy was necessary in 4 of them. The incidence of idiopathic interstitial pneumonia in our group of patients was low (two cases). Also tested was an experimental protocol for the treatment of chemotherapy-resistant metastatic solid tumours. After removal of all clinically detectable tumour tissue by maximal surgical therapy in 5 patients, residual systemic metastases were treated by means of total body irradiation and high-dose cyclophosphamide, followed by autologous bone marrow transplantation with curative intention. Relapse occurred in 4 patients between day 100 and 720 after BMT bone marrow transplantation. Only one patient remains without sign of relapse.