Bronchoalveolar lavage (BAL) was performed to investigate pulmonary involvement in 39 patients with rheumatoid arthritis (RA) and in 7 patients with RA and secondary Sjögren's syndrome, and compared to 12 healthy controls. Lymphocytosis (more than 15%) was seen in 25, and more than 3% neutrophil granulocytes in 8 of 39 patients with RA. Lymphocytosis and/or neutrophil granulocytosis was seen in both seropositive and seronegative patients irrespective of clinical or radiologic findings. Patients with RA with or without secondary Sjögren's syndrome had increased DR+ lymphocytes in BAL compared with peripheral blood. In 7 patients with secondary Sjögren's syndrome an increased helper/suppressor cell index (OKT4+/OKT8+: 7.65 +/- 2.10) and increased natural killer cells (OKNK+: 27.3 +/- 5.5%) were found, as compared to 39 other patients with RA (OKT4+/OKT8+: 2.16 +/- 0.33, p less than 0.05; OKNK+: 14.5 +/- 2.3%, p less than 0.05). These BAL data are further evidence of frequent subclinical interstitial pulmonary involvement in RA with differences in the active autoimmune process from those in secondary Sjögren's syndrome.