A case of a 24-year-old male with fatal cerebro-renal oxalosis assumed to be due to infusions of the sugar surrogate xylitol after appendectomy is reported. The diagnosis was established only after intensive histological investigations following the autopsy. The clinical picture was characterized by an acute seizure, coma and renal failure 2 days after the first xylitol infusion. Death occurred due to cerebral dysregulation as a very rare complication after parenteral administration of xylitol. Subendothelial double refractive calcium oxalate crystals were found in the walls of cerebral blood vessels, in particular in the stem ganglion regions and in the cortical renal tubules. The most common type of primary oxalosis was excluded by sequencing analysis. The young age, the minor surgical intervention and the otherwise unremarkable history are special features of this case. Since the genetic background of xylitol intolerance is still unclear, it is suggested that it should be banned as a sugar surrogate in clinical practice.