This study was designed to investigate by bronchoalveolar lavage (BAL) the characteristics of lung involvement in rheumatoid arthritis (RA). Twenty six patients with RA were included; ten were active smokers. Chest X Ray, pulmonary function tests and BAL were performed in all patients. Bronchiolitis was found in 7% of cases, pleurisy in 30% of cases. 83% of patients were found to have diffuse alveolar and/or interstitial disease, 17% rheumatoid nodules. Functional evaluation showed a restrictive pattern and a significant reduction in the carbon monoxyde diffusing capacity. Smokers had elevated BAL macrophages and decreased lymphocytes compared with non-smokers: respectively 89% vs 62.9% and 7.3% vs 18.9%. Patients with bronchiolitis had lower FVC than others: 38 +/- 14% vs 61 +/- 3%, and their BAL neutrophils were increased: 71 +/- 23% vs 7.5 +/- 2%. There was an inverse correlation between neutrophil counts and FVC in non-smokers, and diffusing capacity. We conclude that BAL inflammatory cells profiles are abnormal in RA and modified by a smoking history and the existence of a bronchiolitis.