Idiopathic pulmonary fibrosis (IPF) and pulmonary fibrosis associated with a collagen vascular disorder (PF-CVD) are chronic inflammatory lung disorders which may be characterized in various subgroups of patients by increased numbers of macrophages, neutrophils, lymphocytes, and/or eosinophils. Previous studies have suggested that the cell populations recovered with bronchoalveolar lavage (BAL) may be important in predicting disease progression and response to therapy. We evaluated this hypothesis in 27 patients by determining if the cell populations recovered with BAL differed between patients who improved, remained stable, or worsened in their pulmonary functions (as defined by at least a 15 percent change in forced vital capacity) over a six-month observation period. The findings suggested that BAL eosinophilia may be a marker of progressive lung disease in patients with IPF and PF-CVD.