Active compounds of some mushrooms e.g. Psilocybe cubensis, Paneolus subalteatus or Stropharia coronilla, the psychotropic agents psilocybin and psilocin, have hallucinogenic effects. In one case of 'magic mushroom' intake, we had to analyse blood and urine. Psilocin was detected in the urine with REMEDi HS. Most of the psilocin was excreted as the glucuronide. Therefore an enzymatic hydrolysis should be the first step in analysis. Free psilocin was determined at a concentration of 0.23 mg/l while the total amount was 1.76 mg/l urine. The concentration of psilocin in serum was too low for detection with REMEDi HS. We proved a GC-MS-method with d(3)-morphine as internal standard and silylation with MSTFA. Similarly to urine, most of the psilocin in serum was found in the conjugated form. The concentration of free psilocin was 0.018 mg/l, that of total psilocin, 0.052 mg/l serum.