Postinfectious bronchiolitis obliterans is a chronic incapacitating disease with persistent airway inflammation. However, the efficacy of systemic corticosteroids has never been studied systematically. In the presented case, serial spirometry, plethysmography measurements, and nocturnal oximetry demonstrated progressive decline in lung hyperinflation and air-trapping and improvement in expiratory function and nocturnal oxygenation during and after six three-day courses of high-dose methylprednisolone (30 mg/kg/day). At four months post treatment, most gain in lung function was lost suggesting the need for sustained immunosuppression. Randomized, controlled trials using serial plethysmography measurements, spirometry, and nocturnal oximetry could provide evidence for the management of postinfectious bronchiolitis obliterans.