A 67-year-old female received a right single lung transplant for idiopathic pulmonary fibrosis and had an uncomplicated post-transplant course; surveillance bronchoscopies did not show acute rejection or infection, and 4 months post-transplantation her FEV1 reached a zenith of 129% of predicted. She remained stable for the next 44 months until diagnosed with BOS (Stage 1). Chest imaging revealed new patchy consolidation in the allograft. Bronchoscopy revealed BAL neutrophilia (28%), and cytomegalovirus was detected in BAL (but not peripheral blood) via polymerase chain reaction. TBB was negative for acute rejection or cytomegalovirus pneumonitis, but showed changes of AFOP. Intravenous pulse methylprednisolone and antibiotics were administered with gradual clearing of the allograft infiltrates on CXR. However, FEV1 continued to decline, and follow-up bronchoscopy 2 months later revealed persistent AFOP and BAL neutrophilia (56%), despite clearing of the allograft infiltrates on CXR. BAL was negative for infection. FEV1 subsequently progressively declined and the patient eventually succumbed to respiratory failure.