Pathogenic rodent-borne hantaviruses cause in humans generalized infections that involve the peripheral vascular bed and severely affect their permeability. We describe a 30-yr-old male patient with clinical symptoms characterizing five conventional phases of hemorrhagic fever with renal syndrome after an uncommonly severe hantavirus infection with the Puumala strain. Renal biopsy in this situation typically demonstrates acute hemorrhagic interstitial nephritis, particularly pronounced in the outer medulla. Hantaviruses are not cytopathic for most cells, and their interactions with endothelial cells that activate immune mechanisms play a key role in the pathogenesis of vascular dysfunction characterizing this disease.