Six patients with rapidly progressive airway obliteration in the absence of chronic bronchitis or emphysema are reported. Because this pattern of lung disease is very uncommon and five of the six patients had classical rheumatoid arthritis an association between the two diseases is suggested. The patients presented with rapidly developing breathlessness, and râles and a high-pitched mid-inspiratory squeak were heard over the lung fields. Chest radiographs showed distended lungs but were otherwise normal. Tests of lung fuction showed airflow obstruction, most marked at low lung volumes, with air trapping. The carbon monoxide gas transfer coefficient, maximum static recoil pressure and static compliance were normal. In spite of treatment with antibiotics, bronchodilators and corticosteroids, five died in respiratory failure five to 18 months after first becoming breathless. Post-mortem examination in four patients showed an obliterative bronchiolitis but no mucous gland hypertrophy or significant emphysema.