We investigated the clinical value of measuring serum concentrations of soluble IL-2R in monitoring sarcoidosis. Serum concentrations of soluble IL-2R were measured in 70 patients with sarcoidosis. The mean value for active untreated sarcoidosis was 1,143 +/- 509 U/ml, while the normal range in 97 healthy control subjects was 80 to 300 U/ml. The mean value for active untreated sarcoidosis was significantly higher than that for dormant disease (353 +/- 183 U/ml) or that for corticosteroid-treated patients (380 +/- 151 U/ml). Serial changes in serum soluble IL-2R level were studied in cases of spontaneous remission or in corticosteroid-treated patients; a good correlation was noted between the changes in serum level of soluble IL-2R and clinical status. A positive correlation was noted between serum concentration of soluble IL-2R and serum ACE activity. These data confirmed that measurement of serum concentration of soluble IL-2R could be used in monitoring the disease activity in sarcoidosis.