The characteristics of patients with rheumatoid arthritis (RA) who develop obliterative bronchiolitis characterised by severe airflow obstruction have been hitherto poorly investigated. A retrospective study of 25 patients with RA and functional evidence of obliterative bronchiolitis (forced expiratory volume in one second (FEV(1))/forced vital capacity (FVC) <50% and/or residual volume (RV)/total lung capacity (TLC) >140% predicted) was conducted. Patients (mean+/-SD age 64+/-11 yrs) included 17 never-smokers and eight ex-smokers (10.5+/-5.4 pack-yrs). The diagnosis of RA preceded respiratory symptoms in 88% of cases. Dyspnoea on exertion was present in all patients and bronchorrhea in 44%. High-resolution computed tomography findings included: bronchial wall thickening (96%), bronchiectasis (40%), mosaic pattern (40%), centrilobular emphysema (56%), and reticular and/or ground-glass opacities (32%). Pulmonary function tests showed: FEV(1) 41+/-12% pred, FEV(1)/FVC 49+/-14%, FVC 70+/-20% pred, RV 148+/-68% pred and RV/TLC 142+/-34% pred. Lung biopsy, available in nine patients, demonstrated constrictive, follicular and mixed bronchiolitis. Patients were followed for 48.2+/-49 months. Treatment was poorly effective. Chronic respiratory failure occurred in 40% of patients, and four patients died. Obliterative bronchiolitis associated with rheumatoid arthritis is a severe and under-recognised condition leading to respiratory failure and death in a high proportion of patients.