A 77-year-old man developed a fever up to 38.4 degrees C, with diarrhoea, acute renal failure (creatinine up to 8.7 mg/dl; urea up to 308 mg/dl) and marked jaundice (total bilirubin up to 24.3 mg/dl). In addition there was thrombocytopenia, conjunctivitis and epistaxis, as well as cerebral symptoms with somnolence and general slowing up. At first he was thought to have cholangitis resulting from previously diagnosed gall-stones, and he was therefore treated with ampicillin, 2 g two times daily, and metronidazole, 0.5 g two times daily. The fewer regressed, but the renal failure required haemodialysis and haemofiltration under strict fluid control. Endoscopy excluded obstructive jaundice, but a suspicion of inflammatory liver disease or possibly cirrhosis was raised in the differential diagnosis. Serology revealed an increased titre for Leptospira interrogans var. sejroe (1:200, later 1:1600). Liver biopsy finding was compatible with the diagnosis of leptospirosis. Because of the high inflammatory activity in the liver, 2 mega units of penicillin G were administered three times daily for six days. Gradually the renal functions and jaundice improved and, on discharge on the 36th day, the patient was again in generally good health, although creatinine and bilirubin values were still slightly elevated (1.7 mg/dl each).