In a group of 20 patients with active pulmonary sarcoidosis and in 20 healthy subjects, serum levels were determined of angiotensin I converting enzyme, immunoglobulins, and of the third and fourth complement components. An increased level of IgG and IgM was found in patients with sarcoidosis, as compared with the control group. High ACE levels were observed in the second and third phase of the disease. A tendency was also observed for simultaneous increase of IgG and ACE levels in patients with sarcoidosis.