The potential for interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) to induce neutrophil and mononuclear phagocyte accumulation in the lungs of patients with pulmonary sarcoidosis and idiopathic pulmonary fibrosis (IPF) was investigated. Bronchoalveolar lavage (BAL) fluids from 12 patients with IPF and 15 with sarcoidosis were concentrated by reversed-phase chromatography, and their IL-8 and MCP-1 concentrations assessed by enzyme-linked immunosorbent assay (ELISA), chemotaxis, and enzyme-releasing assays with monocytes and neutrophils. ELISA revealed significantly elevated concentrations of MCP-1 (20.1 ng/mg albumin) in the BAL fluids of patients with pulmonary sarcoidosis and those with IPF (41.8 ng/mg) in comparison to 11 normal individuals (4.24 ng/mg) and 15 patients with chronic bronchitis (CB) (5.16 ng/mg). Similarly, the chemotactic activity for monocytes (MCP-1 equivalent) was strongly increased in patients with sarcoidosis (86.03 ng/mg) as well as in those with IPF (54.47 ng/mg). The chemoattractant activity of normal individuals and CB patients was 7- or 3-fold lower, respectively. Patients with IPF and sarcoidosis also had elevated IL-8 levels (15.5 and 26.0 ng/mg, respectively; normals: 2.14 ng/mg; and CB patients: 4.23 ng/mg) and greater neutrophil chemotaxis (60.25 and 49.68 ng/mg, respectively; normals: 0.35 ng/mg; and CB patients: 11.06 ng/mg). These data suggest that increased levels of both MCP-1 and IL-8 may be characteristic for sarcoidosis or IPF. It appears likely that both of these chemoattractants contribute to the influx of monocytes and neutrophils into the pulmonary alveolus and interstitium in these diseases.