Angiotensin-converting enzyme (ACE) genotypes may reflect prognosis in sarcoidosis. They were determined in 59 Finnish sarcoidosis patients and 70 healthy control subjects. The prognosis of the sarcoidosis patients was determined after follow-up for 1, 2, 3, 5 and >5 yrs and classified as good (normal chest radiograph and lung function, no signs of extrapulmonary disease activity within 2 yrs from diagnosis), intermediate (neither good nor poor) or poor (persisting unstable pulmonary infiltrates, vital capacity and diffusing capacity of the lung for carbon monoxide <50% predicted and/or extrapulmonary disease activity after >5 yrs follow-up). The DD, ID and II genotypes were found in 31 and 27%, in 54 and 49%, and in 15 and 24% of patients and control subjects respectively. The odds ratio (DD+ID to II) was 1.45 (95% confidence interval 0.60-3.49). The D alelle was found more often in patients (58%) and in control subjects (51%) than the I allele but the difference was not statistically significant. Statistically significantly more patients with the DD genotype had a poor prognosis compared with patients with II homozygotes and ID heterozygotes. Among 11 patients with Löfgren's syndrome (bilateral hilar lymphadenopathy and erythema nodosum), four had the DD genotype. Three of these patients had a prognosis despite presenting a clinical picture usually associated with a good prognosis. The angiotensin-converting enzyme genotype may be a prognostic marker in sarcoidosis and larger studies are warranted to define its clinical utility.