Acute renal failure in Legionnaires' disease is rare, but the mortality rate is high [1-3]. Although the actual pathogenesis is not clear, the renal pathology discloses either acute tubulointerstitial nephritis or acute tubular necrosis in most cases [3]. We report two cases of Legionnaires' disease complicated by acute renal failure. One patient was completely healthy before, and the other had underlying gouty arthritis and diabetes mellitus. Their renal function was normal before these episodes. The diagnosis of Legionella infection was proved by the indirect fluorescent antibody test on paired sera. After erythromycin treatment, both patients survived. One patient required long-term maintenance hemodialysis, and the other recovered to only mild azotemia after a follow-up period of 5 months. Including our cases, only 55 patients have been reported to have Legionella-induced acute renal failure. This is a rare and serious complication of Legionnaires' disease. Early recognition and treatment is mandatory.