Interstitial pulmonary fibrosis is a common feature of systemic sclerosis (SS). Clinicopathologic observations suggest that interstitial and alveolar inflammation may appear prior to fibrosis. Using the bronchoalveolar lavage (BAL) technique, we have characterized the nature of the inflammatory process in the lower respiratory tract of 15 non-smoking scleroderma patients and compared the results with those found in eight normal subjects. Alveolitis was detected in 11 patients (73%). Abnormalities in the cellular constituent included a significant increase of the proportion of lymphocytes (20.8 +/- 3.2 vs 8.1 +/- 1.2; p = 0.01) and neutrophils (3.3 +/- 0.8 vs 0.8 +/- 0.2; p = 0.04). T cell subsets, evaluated by flow cytometry, showed a significant increase of CD8+ T cells (36.6 +/- 3.2 vs 25, 1 +/- 3.3; p = 0.04) and a decrease of CD4+/CD8+ ratio (1.1 +/- 0.1 vs 2.1 +/- 0.4; p = 0.04). Seven patients with an elevation of proportional BAL (lymphocyte count > 15%) had greater dyspnoea and chest radiographic score than patients without lymphocytic alveolitis (p = 0.02) and they had greater reduction in carbon monoxide diffusing capacity (DLco) (p = 0.04). Furthermore, a statistically significant correlation between the total lymphocyte cell count and the DLco (p = 0.03) was observed. Finally the stepwise multiple regression analysis identified lymphocyte count in lavage fluid as the predictor most strongly associated with an abnormal interstitial radiographic pattern (p = 0.001). Our results report the notion that the lymphocytes, in addition to the macrophages and neutrophils, may play roles in the pathogenesis of lung injury.