A 37-year-old man developed delayed non-infectious lung disease after undergoing bone marrow transplantation (BMT) for acute myeloid leukaemia. Over a 15-month period, the progression of morphologic changes from cellular interstitial pneumonia to bronchiolitis obliterans organizing pneumonia and cicatricial bronchiolitis obliterans was documented. Pulmonary function tests, high-resolution CT, bronchoalveolar lavage, lung biopsy and extensive microbiological studies were used as diagnostic tools either at onset and during the follow-up. This represents the first reported case in which a model--supported by longitudinal biopsy results--for the evolution of histologic lesions toward bronchiolitis obliterans after BMT is suggested; therapeutic implications are discussed.