A number of the wild Danish mushrooms contain the hallucinogenic agent psilocybin which resembles LSD in many ways. The commonest of these are the "liberty cap" or "magic mushrooms" (Psilocybe semilanceata). On the basis of experience from USA and western Europa, increase in employment of this mushrooms as a hallucinogenic intoxicant may be anticipated in Denmark. The history, epidemiology, botany and pharmacology of the mushroom are reviewed. Clinical pictures and treatment are described for: 1) Acute poisoning with psilocybin-containing fungi, 2) Late sequelae of consumption of psilocybin-containing fungi and 3) Poisoning with more poisonous fungi on account of incorrect identification. General practitioners, duty roster doctors, doctors in casualty departments and in acute psychiatric departments should be aware of these problems. Intoxication with psilocybin may be confused with panic anxiety or euphoria in persons with mydriasis and other sympathomimetic symptoms. The possibility of more serious mushroom poisoning on account of incorrect identification should be borne in mind.