The toxicological importance of Paxillus involutus is discussed controversially. Therefore it is necessary to give a critical review about this problem. In the mycological literature printed before 1970 Paxillus involutus was estimated as an edible mushroom of well taste. The only premise to avoid an toxication with gastrointestinal symptoms was the destruction of heatlabile toxins by heating the mushroom longer than 20 minutes. Despite the mushroom were heated long enough, between 1940 and 1960 the number of severe intoxication caused by Paxillus involutus increased. The German mycologist J. Schaffer died after an ingestion of Paxillus involutus whereas all other participants of the meal did not show any symptoms of an intoxication. The mushroom intoxications recorded between 1961 and 1989 in the former GDR showed an increase of intoxications with Paxillus involutus till 1976. After an action of instructing people the number of intoxications decreased again. Investigations of Deicher and Strangel (1977) and Winkelmann et al. (1986) showed that in the region of Hannover about half of the population of Paxillus involutus contained an unknown antigen, which causes a so called “immunehaemolytic anaemia” including following symptoms: Vomiting, abdominal pain, circulatory shock, icterus, haemolysis, anuria and pulmonary failure. A repeated contact induces the production of IgG which is liberated by a following ingestion, inducing haemolysis and the other above effects. The mushrooms containing the antigen and those without antigen can only be discriminated by specific immunological methods. It is concluded that the use of Paxillus involutus as human food is dangerous because of the risk of a sensibilization followed by an immunehaemolytic anaemia. The possible reasons of the increase of the “Paxillus syndrome” and the territorial distribution of the dangerous variant of Paxillus involutus are discussed.