Among poisonous mushrooms, a small number may cause serious intoxication and even fatalities in man. Humans may become symptomatic after a mushroom meal for rather different reasons: (1) ingestion of mushrooms containing toxins, (2) large amounts of mushrooms may be hard to digest, (3) immunological reactions to mushroom-derived antigens, (4) ingestion of mushrooms causing ethanol intolerance, and (5) vegetative symptoms may occur whenever a patient realizes that there might be a possibility of ingestion of a toxic mushroom after a mushroom meal. Based on the classes of toxins and their clinical symptoms, seven different types of mushroom poisoning can be distinguished: (1) phalloides, (2) orellanus, (3) gyromitra, (4) muscarine, (5) pantherina, (6) psilocybin, and (7) gastrointestinal mushroom syndrome. Two other entities of adverse reactions to mushrooms are (8) coprinus and (9) paxillus syndrome. Phalloides, orellanus, gyromitra and paxillus syndrome may lead to serious poisoning, which generally requires treatment of the patient in an intensive care unit. Diagnosis of mushroom poisoning is primarily based on anamnestic data, identification of mushrooms from leftovers of the mushroom meal, spore analysis, and/or chemical analysis. Therapeutic strategies include primary detoxification by induced emesis, gastric lavage and activated charcoal, secondary detoxification, symptomatic treatment and rarely specific antidotes. Owing to progressing fulminant hepatic failure, lethality associated with phalloides syndrome is still high (5-20%). Basic treatment includes administration of silibinin and penicillin G, although controlled studies on its therapeutic efficacy are still lacking. In serious phalloides syndrome, orthotopic liver transplantation has to be considered. Fortunately, the prognosis in most other mushroom poisonings is excellent.