Between 1980 and 1986 we transplanted 49 patients from genotypically identical sibling donors for severe aplastic anaemia (SAA). Patients were predominantly adults, median age 22 years (3-47). Forty-six were multiply transfused prior to referral. The median pre-transplant disease duration was 4 months (1-72). Pre-transplant conditioning was with cyclophosphamide (CY) 200 mg/kg. Cyclosporin A (CSA) was given from 1 day before the transplant and continued for 9-12 months. Eight of 48 evaluable patients did not achieve initial engraftment (early graft failure). Six of these episodes occurred in the eight cases transplanted more than 1 year after diagnosis, four of whom died. Thirteen of 44 (30%) evaluable patients (with stable engraftment after one or two transplants) had grade III-IV acute graft-versus-host disease (GVHD). Only three of 35 patients surviving more than 100 days with sustained engraftment developed generalized chronic GVHD; two died. An additional 10 patients developed localized chronic GVHD, which was very mild, transient and related to CSA withdrawal. Four long-term survivors are known to have autologous marrow function. All survivors have Karnofsky scores of greater than 90%. We conclude that the use of CSA after bone marrow transplantation for SAA is associated with good long-term survival and minimal on-going chronic GVHD. Early graft failure was frequent when transplantation was delayed beyond 1 year from diagnosis.