Chronic renal failure has never been described after Puumala hantavirus infection, which usually causes acute renal failure with spontaneous full recovery. We report a 15-year-old boy who presented with Puumala hantavirus infection and initial severe acute renal failure. His renal function gradually improved, but more than 2 years after the acute episode it was still moderately impaired, with a creatinine clearance of about 60 ml/min per 1.73 m(2)