The production of interleukin-1 (IL-1) in alveolar macrophages (AMs) was studied in 25 patients with sarcoidosis to inversigate the role of immune mechanisms in this disease. The radioimmunoassay (RIA) method was compared with the bioassay method for detecting IL-1 in the supernatants of AM cultures. The level of IL-1β measured by RIA was closely corrrelated with the IL-1 activity measured by bioassay (r=0.88, p<0.01). The amount of IL-1β in the supernatant of AM cultures from sarcoidosis patients was compared with those from control subjects. No significant IL-1β activity was detected in the culture supernatants of unstimulated AMs from either group of subjects. However, the production of IL-1β by AMs stimulated with Propionibacterium acnes (P. acnes) was significantly higher in patients with sarcoidosis than in controls (p<0.05). Lipopolysaccharide (LPS) induced increased IL-1β production by AMs from both sarcoidosis patients and controls compared to unstimulated or P. acnes-stimulated AMS, but the mean IL-1β level for sarcoidosis AMs did not differ from that for control AMs. There was no difference in the IL-1β production of peripheral blood monocytes between sarcoidosis patients and controls. These data suggest that AMs are activated in sarcoidosis and may modulate alveolar lymphocyte functions to play a critical role in the pathogenesis of the disease.