In 14 patients with pulmonary sarcoidosis and 14 matched controls we studied peripheral blood lymphocyte and monocyte counts, distribution of T and B lymphocytes, the functional helper:suppressor T cell balance, the antibody-dependent cell-mediated cytotoxicity of monocytes (monocyte ADCC), and the capacity of peripheral monocytes to generate angiotensin converting enzyme (ACE) in culture. Apart from lymphopenia in sarcoidosis patients we found a normal lymphocyte subset distribution and no evidence of increased suppressor T cell activity, using a PWM driven proliferative assay. The patients exhibited a normal monocyte count, but the proportion of monocytes was increased in sarcoidosis. Patients with active sarcoidosis had a significantly increased monocyte ADCC which was positively correlated with raised serum ACE. Peripheral monocytes had a measurable, but low ACE activity, which was modestly higher in active sarcoidosis than in controls. We could not reproduce earlier reported results on a glucocorticoid induced ACE synthesis from cultured human monocytes.