Fibrosing alveolitis (FA) is a major and often fatal complication of systemic sclerosis (SSC). The critical role of fibroblasts in the pathogenesis of FA has long been recognized. Characterization of fibroblast activation in the lungs may improve our understanding and the management of this disease. We analyzed bronchoalveolar lavage (BAL) fluid samples from 9 healthy controls and 43 patients with FA caused by lung involvement form SSC. The chemoattractant activity (CAA) of cultured human fibroblasts elicited by native BAL fluid was measured in Boyden chambers. In addition, procollagen III peptide was measured in BAL fluid as a marker of collagen synthesis. CAA (expressed as percentage of the chemoattractant effect of 0.25 ng/ml platelet-derived growth factor; PDGF) was elevated in the SSC patients compared with that of the controls (control: 12.6 +/- 4.0%; SSC: 68.8 +/- 15.2%; p < 0.01). A positive correlation was found between BAL total cell count and CAA (r = 0.60, p < 0.01). An inverse correlation existed between CAA and total lung capacity (r = -0.55, p < 0.05). The patients were followed up for 13.3 +/- 1.4 months (mean +/- SEM). Twenty-seven patients received immunosuppressive therapy, whereas 16 refused therapy. The patients were assigned to two groups according to their CAA being lower or higher than 36% of the PDGF response (= mean value of the controls + 2 SD).