Summary:Bronchiolitis obliterans (BO) is a rare but serious complication of paediatric allogenic bone marrow transplantation (BMT). Currently, there is no clear evidence that therapeutic interventions have a positive impact on the course of the disease. We here report our experience with high-dose pulse methylprednisolone therapy in children after BMT. Nine patients fulfilling clinical and radiologic signs of BO were included in this analysis. The total amount of treatment cycles with pulse methylprednisolone therapy ranged from 1 to 6 cycles (median four cycles). Oxygen saturation increased significantly with normalization of oxygen saturation at the end of therapy in all individuals. Normal oxygen saturation was maintained in all but one patient during follow-up (mean follow-up period 42 {plus/minus} 20 months, range 19-67 months). Forced expiratory volume in 1 s (FEV1) was within the normal range prior BMT and significantly diminished at the time of BO diagnosis. Treatment led to stabilization of lung function, with a significant improvement of FEV1 after 2 months. In all, 7/9 patients remained in clinically stable condition without further deterioration of lung function during follow-up. These data would suggest that anti-inflammatory therapy may be a valuable treatment option in paediatric patients with bronchiolitis obliterans after BMT. Bone Marrow Transplantation (2005) 36, 135-138.