Superoxide anion release (O2-) after stimulation with phorbol myristate acetate was measured in alveolar macrophages (AM) obtained by bronchoalveolar lavage and in blood monocytes from 47 patients with diffuse interstitial lung disease: idiopathic pulmonary fibrosis (N = 15), hypersensitivity pneumonitis (N = 7), pneumoconiosis (N = 6) and sarcoidosis (N = 19). Differential cell counts demonstrated a lymphocyte predominance in patients with hypersensitivity pneumonitis (HP) and sarcoidosis while the other groups had neutrophil predominance. No correlation between O2- activity in alveolar macrophages (AM) or blood monocytes (BM) compared to lung function (VC and diffusing capacity) could be demonstrated. Smoking pneumoconiotics had significantly decreased BM O2- release (1.25 +/- 0.25 (SEM) nmol/min/10(6) cells) and significantly increased AM/BM O2- ratios (2.04 +/- 0.26) compared to smokers with idiopathic pulmonary fibrosis (IPF) who had the following mean values: BM O2- release = 2.58 +/- 0.25 and AM/BM O2- ratio = 0.86 +/- 0.23. When matched for sex and smoking, a significantly increased AM/BM O2- ratio was seen among patients with HP (2.19 +/- 0.98) in comparison with patients who had sarcoidosis (0.40 +/- 0.18). Patients with either HP or pneumoconiosis had generally elevated AM O2- release and reduced BM O2- release. These results suggest that environmentally related interstitial lung disorders (HP and pneumoconiosis) may be associated with elevated AM O2- release relative to BM O2- release in comparison to non-environmentally related disorders (IPF or sarcoidosis).