A 29-year old man was admitted to our hospital due to low-grade fever and abnormal pulmonary shadows in May 2001. Laboratory findings revealed an elevated serum ACE up to 39.7IU/l and uveitis was also noted. Chest X-ray film showed bilateral lymphadenopathy and patchy shadows scattered in the bilateral lung fields. A transbronchial lung biopsy (TBLB) demonstrated epithelioid cell granulomas, compatible with sarcoidosis. Serum creatinine gradually elevated although pulmonary lesions almost disappeared without treatment. A specimen of percutaneous renal biopsy demonstrated epithelioid cell granulomas with Langhans giant cells, tubular atrophy and fibrosis in the interstitium, corresponding with granulomatous interstitial nephritis. Renal function improved after corticosteroid therapy, but was not completely recovered. It should be kept in mind that granulomatous interstitial nephritis due to sarcoidosis could cause renal failure unless treatment is started at an early stage.