Cellular immune response is accompanied by the release of neopterin. Increased neopterin levels in urine and serum are observed in patients during viral infections, autoimmune diseases, and allograft rejections and certain malignant diseases. We investigated postmortem neopterin concentrations in urine and serum samples taken from 32 corpses 3 to 69 h (mean 19.3 h) after death. Urine neopterin concentrations in corpses are similar to those of healthy live controls and are independent of the time after death. In contrast, serum neopterin concentrations are frequently greatly increased in corpses, and the levels are higher in sera collected more than 10 h after death in comparison with samples obtained earlier. Neopterin measurement in urine and serum samples of corpses is feasible. It appears likely that urine neopterin concentrations could aid the diagnosis of inflammatory diseases in corpses.