The angiotensin-converting enzyme (ACE) has been implicated in the pathophysiology of sarcoidosis. Serum ACE levels in normal and sarcoidosis patients are influenced by an insertion (I)/deletion (D) polymorphism in the ACE gene. To elucidate the role of this ACE gene polymorphism in sarcoidosis, we conducted a case-control study in African Americans and Caucasians. The ACE gene (I/D) polymorphism did not differ between 60 Caucasian cases and 48 control subjects (p = 0.577). In contrast, a comparison of 183 African-American cases and 111 control subjects resulted in a marked difference in genotypic distributions (p = 0.005). In African Americans, the risk for sarcoidosis was 1.30 (95% confidence interval [CI] = 0.72 to 2.36) for ID heterozygotes, and 3.17 (95% CI = 1.50 to 6.71) for deletion/deletion (DD) homozygotes. The risk associated with the DD homozygotes was even greater in African Americans when cases were restricted to those with a positive family history (odds ratio = 4.83; 95% CI = 1.86 to 12.59). Further analyses of African-American cases showed that the ACE genotype was not associated with disease severity, extrathoracic involvement, or overall radiographic change 2 to 4 yr after diagnosis. We did find a moderate association between the II genotype and radiographic progression (OR = 2.97; 95% CI = 1.01 to 8.76). Our results suggest the ACE genotype may play a more important role in sarcoidosis susceptibility and progression in African Americans than Caucasians.