Peripheral blood lymphocytes frm 16 patients with sarcoidosis (9 patients with skin sarcoids, 7 patients with erythema nodosum and bilateral hilar adenopathy) and cutaneous anergy and from 23 age-matched healthy controls were characterized by reactivity with monoclonal antibodies OKT3, OKT4, OKT8 directed to surface antigens of T lymphocytes, helper-inducer and suppressor-cytotoxic T cell subsets, respectively. In contrast to healthy controls, patients with sarcoidosis had reduced percentages of OKT3+, OKT4+ and OKT8+ cells and a major decrease in the OKT8+ (suppressor) subset. However, these changes were significant only in the group of patients with acute sarcoidosis (erythema nodosum). This abnormal T cell distribution correlates with the alterations in cell-mediated immunity previously observed and suggests the presence of a defective circulating suppressor T cell activity in acute sarcoidosis.