AIMS/BACKGROUND--The aetiology of Fuchs' heterochromic uveitis (FHU) is unknown although it can occur in combination with a number of different ocular conditions. Five patients with FHU who show an association with sarcoidosis were studied. METHODS--Four patients with clinical signs compatible with FHU who had elevated serum angiotensin converting enzyme levels (sACE), and a fifth case with a normal sACE and a positive Kveim test were described. RESULTS--All five cases had iris nodules, two later developed mutton fat keratic precipitates, and one had peripheral retinal periphlebitis. Of the four cases with elevated sACE, one had respiratory function test abnormalities and an abnormal chest x ray compatible with pulmonary sarcoidosis. Another had a chorioretinal scar and developed intermediate uveitis 2 years after presentation. CONCLUSIONS--In all of these cases a diagnosis of FHU may represent a specific secondary ocular response to sarcoidosis rather than a primary idiopathic uveitis syndrome. Although FHU remains a clinical diagnosis, routine uveitis investigations should still be performed in this group of patients.