Chronic rejection (obliterative bronchiolitis) is the single most important cause of chronic allograft dysfunction and late mortality after lung transplantation. As this condition is difficult to prove using biopsy specimens, a clinical term, bronchiolitis obliterans syndrome (BOS) has been in use for >10 yrs to describe the progressive decrease of pulmonary function. However, before diagnosing a patient as having BOS, based on a sustained and progressive decrease in forced expiratory volume in one second and/or forced mid-expiratory flow between 25-75% of forced vital capacity, different confounding factors have to be eliminated. Treatment of BOS mainly consists of an increase or a change in the immunosuppressive drug regimen, which may lead to more pronounced infectious complications. Recently, two new options have become available to treat patients with BOS, treatment of gastro-oesophageal reflux and azithromycin. In the present paper, the authors give an overview of the current data on these two modalities, which may lead to a restoration of the pulmonary function in some of the patients, illustrating once more the fact that bronchitis obliterans syndrome is not always a manifestation of chronic rejection.