We report a series of 19 cases of bronchiolitis obliterans with organized pneumonitis (BOOP) observed in two pneumology units at the Strasbourg University Hospital between July 1987 and June 1997. Mean patient age was 60 years. Clinical features included dry cough, exercise-induced dyspnea, and a flu-like syndrome in three-quarters of the cases. Standard chest x-ray showed a diffuse non-systemized alveolar syndrome with a air bronchogram in 18 cases and an interstitial syndrome in one-third of the cases. computed tomography of the thorax visualized bronchial dilatations by traction of the alveolar syndrome in one-third of the cases. Pulmonary function tests showed moderate restriction. Lymphocytes predominated in bronchio-alveolar lavage fluid. Pathology examination of surgical lung specimens (5 cases), transbronchial biopsies (5 cases) and scan-guided transparietal punctures (4 cases) provided the diagnosis. In 5 cases the diagnosis was based on the radiological and clinical presentation and favorable course on corticosteroid therapy. Recurrence was observed at corticosteroid withdrawal or dose reduction in 7 cases. In this series, bronchiolitis obliterans with organized pneumonitis was probably secondary to rheumatoid arthritis (1 case), breast radiotherapy (3 cases), and drugs (amiodarone: 1 case: sotalol: 2 cases: betaxolol: 1 case). An association with betaxolol has not been previously reported in the literature.