In a group of control subjects, the mean serum angiotensin‐converting enzyme (ACE) level was 38.1 ± 10.6 nmol/min • ml (n = 30), and in a group of silicosis patients the mean serum ACE level was 45.2 ± 76.0 (n = 26). Thirteen of these patients were classified as having nodular silicosis, and their mean serum ACE level was 44.2; 10 of these patients were classified as having progressive massive fibrosis, and their mean serum ACE level was 39.4. Three of these patients had confirmed silicotuberculosis, and their serum ACE levels were 63, 67, and 77 (mean = 69) these serum ACE levels are somewhat higher than those having been reported for patients with acute sarcoid‐osis. Thus, when serum ACE levels are being used to assist in distinguishing between silicosis and sarcoidosis, the possibility of silicotuberculosis must be also considered when high serum ACE levels are encountered.