An assessment of immune function was performed in twenty-four patients with recently diagnosed active sarcoidosis. Four patients manifested skin anergy to four antigens. All subjects except one were capable of generating a positive skin response to a croton oil patch test. The incorporation of [3H]thymidine by lymphocytes in vitro in response to the nonspecific mitogens--phytohaemagglutinin, pokeweed mitogen and Con A did not differ between anergic and non-anergic thymidine incorporation in vitro when stimulated by the specific antigens, streptokinase/streptodornase or Candida albicans. Lymphocytes obtained from nine of eleven patients having positive delayed hypersensitivity skin reactions demonstrated MIF production in vitro upon specific antigen challenge. Quantities of circulating B and T lymphocytes did not differ between anergic and absolute numbers of circulating B and T lymphocytes, as well as hypercomplementaemia and hypergammaglobulinaemia when compared to the control group.