Phagocytosis and killing activities of alveolar macrophages were compared in 17 patients with stage 1 sarcoidosis and 6 healthy controls. The average total cell count of bronchoalveolar lavage fluid from patients with sarcoidosis was 7.8 -+ 7.5 x 106 cells; 70.4 -+ 15% of these cells were alveolar macrophages and 25.9 _+ 16.2% lymphocytes. Average total cell count from controls was 8.33 -+ 8.6 x 106 cells, with 92.7 --_ 5.9% alveolar macrophages and 6.6 ---4.4% lymphocytes. Purified alveolar macrophages were tested in in vitro antibacterial assays using S. aureus as a test microbe. Moderate decreases in the kinetics of staphylococcal ingestion were detected in the sarcoidosis group. The intracellular killing activity of macrophages was much lower in the patients with sarcoid than in control subjects. In a pilot study, intracellular killing activity of macrophages from 1 patient with sarcoidosis was greatly enhanced by 24 hr treatment with transfer factor. In summary, alveolar macrophages from patients with radiographic stage 1 sarcoidosis have decreased bacterial ingestion and intracellular killing activities. These results suggest that macrophages undergo complex functional changes in sarcoidosis that may influence both disease development and host defenses.