Background.Bronchiolitis obliterans (BO) is the most important long-term complication of lung transplantation. Treatment of this condition is often unsuccessful.Methods.A patient presented with early BO. Despite OKT3 and the addition of methotrexate, the patient needed persistently high doses of prednisone to maintain lung function at a moderate level. Only the substitution of azathioprine by mycophenolate mofetil (MMF, 3 g/day) made it possible to reduce the dose of prednisone.Results.Reduction of the dose of MMF to 2 g/day resulted in a deterioration of lung function, which improved impressively after MMF was increased again to 3 g/day.Conclusions.MMF may be a valuable therapy for lung transplant BO. However, the use of a high dose, i.e., 3 g/day, may be crucial.