Allogeneic bone marrow transplantation (BMT) is the treatment of choice in young patients (pts) with severe aplastic anemia (SAA) who have an HLA identical sibling donor. Late graft rejection to following allogeneic BMT for SAA is a significant clinical problem and is associated with a high risk of mortality. The optimal treatment strategy for patients with late graft rejection after first BMT is still an open question. We report 12-year-old patient with acquired SAA who underwent BMT from his HLA identical sister. BMT was first-line treatment within 3 months of diagnosis. Preparative therapy was Cyclophosphamide (Cy) 200 mg/kg body mass (BM) during 4 days. Graft versus host disease (GVHD) was prevented with Methotrexate (MTX), Methylprednisolone (MPDN) and Cyclosporin A (CsA). After 17 months, during which patient was with normal blood counts and full donor chimaerism, graft rejection occurred. The patient was re-engrafted from the same donor after conditioning with Cy 200 mg/kg BM plus horse antithymocyte globulin (ATG)--2 vials (á 25 mg)/10 kg BM over 4 days. Before the collection, donor's bone marrow was activated with low dose rhGM-CSF (3 micrograms/kg one day). Following a secondary BMT engraftment has sustained. The patient is alive with full donor chimaerism 26 months from secondary transplantation, without acute or chronic GVHD.