Summary:With improvement in long-term survival after allogeneic stem cell transplantation, late complications with significant morbidity are of increasing importance. We retrospectively analysed 272 recipients of an allogeneic stem cell transplant for the development of osteonecrosis. The incidence among allograft recipients was 6.3% (17/272) for the whole patient population, and 11.8% (17/144) for long-term survivors. All patients were treated with high-dose prednisolone, 16 for severe acute or extensive chronic graft-versus-host disease (GVHD) and one patient for graft rejection. The mean age at time of diagnosis was 33 years (range 16-45) and the mean time from transplant to diagnosis of osteonecrosis was 13 months. Osteonecrosis was diagnosed by magnetic resonance (MR) imaging, which allows early detection of osteonecrosis and assessment of stage. At the time of diagnosis, eight patients had stage I, three patients stage II, three patients stage III and three patients stage IV osteonecrosis according to MR criteria. All but one patient had involvement of the femoral head. The median total dosage of prednisolone at the time of diagnosis was 189 mg/kg (single manifestation 150 mg/kg; multiple manifestations 313 mg/kg) with a total range of 13-555 mg/kg. Six patients were treated by conservative means, 77 patients underwent surgery (three core decompression, eight joint replacement). MR screening of patients receiving highdose steroids might help to detect osteonecrosis at an early stage and thus prevent progression by early intervention, for example, by core decompression. Keywords: avascular necrosis; allogeneic stem cell transplantation; magnetic resonance-steroids With improvement in long-term survival after allogeneic bone marrow transplantation, late complications with significant morbidity are of increasing importance.Osteonecrosis is a general term applied to conditions resulting in necrosis of bone and marrow elements. Avascular necrosis indicates involvement of the epiphysis or subCorrespondence: Dr H Einsele, Department of Hematology and Oncology, University of Tübingen, Otfried Müller Str. 10, 72076 Tübingen, Germany Received 9 March 1998; accepted 20 April 1998 chondral bone, whereas osteonecrosis of the metaphyseal or diaphyseal bone is commonly referred to as bone infarct.