Current concepts of the immunopathology of sarcoidosis indicate that activated pulmonary T-lymphocytes play a central role in the maintenance of inflammatory processes. For the clinical management of the disease parameters which reflect the compartmentalized T-cell activation in the lung and which can be obtained from the peripheral blood are desired. Activated T-cells are known to release sIL-2R. Thus, we hypothesized that in pulmonary sarcoidosis disease activity could be monitored by the measurement of serum levels of sIL-2R. Our results demonstrate that disease activity is reflected more accurately by the serum level of sIL-2R than that of ACE, suggesting that phenomena of T-cell activation determining the course of the disease are monitored by this approach.