In August 1995 a 23-year-old man was admitted to the hospital because of acute anuria. 14 days prior to admission he had consumed five fruit bodies of raw mushrooms of the Cortinarius speciocissimus species. The tentative diagnosis of acute renal failure due to orellanine intoxication was confirmed by the histologic finding of an acute interstitial nephritis in a first renal biopsy one week after onset of anuria. The patient required hemodialysis for the following weeks and months, is now on peritoneal dialysis and is awaiting renal transplantation. Six months after onset of symptoms a second renal biopsy was performed, which revealed increasing interstitial fibrosis. In contrast to the findings of Rapior et al. 1989, orellanine could not be detected in this specimen. The negative toxin test in this second renal biopsy is possibly explained by a wide variability of pharmacokinetics of orellanine.