Bronchoalveolar lavage (BAL) was performed to assess the nature of pulmonary involvement in 12 asymptomatic nonsmoking patients with rheumatoid arthritis (RA). All 12 patients had normal lung function tests, including diffuse capacity for carbon monoxide and normal blood gases. Four patients (33%) had mild basilar interstitial changes on chest radiographs. In these 4 patients an elevated lymphocytic count in BAL fluid (30.7 +/- 8.3%) was found, as compared to the 8 patients with normal chest roentgenograms (7.2 +/- 1.9%; p less than 0.001). We suggest that BAL may be used as a sensitive tool for early diagnosis of pulmonary involvement in patients with RA.