sICAM‐1 has been elevated in sera of specific inflammatory diseases, and circulating sICAM‐1 concentrations reflect disease activity in these diseases. We measured circulating sICAM‐1 concentrations and serum angiotensin‐converting enzyme (SACE) activity in patients with sarcoidosis. Patients with sarcoidosis had significantly increased circulating sICAM‐1 concentrations (62.8±33.5U/ml) and SACE activity (23.7±7.4U/l) compared with controls (circulating sICAM‐1 50.9±12.1U/ml, and SACE 13.5±3.8U/l). Successive measurements showed that circulating sICAM‐1 values changed in parallel with disease activity in sarcoidosis. In the progressive disease group (progressed or without change for 2 years or more), circulating sICAM‐1 values (102.2±35.3U/ml) at the time of diagnosis were significantly increased compared with those in the regressive disease group (disappeared or regressed within 2 years) (46.4±12.6U/ml). However, there was no significant difference in SACE activity of the regressive and progressive disease groups. Fifteen patients with a high value of circulating sICAM‐1 (>75U/ml, mean of controls+2s.d.) all had progressive disease, while only 15 of 44 patients with a high value of SACE had progressive disease. Circulating sICAM‐1 will be a useful blood marker to predict outcome and to monitor disease activity in sarcoidosis.