Poisonous mushrooms contain toxins that are as diverse as the mushrooms themselves. Clinical syndromes often involve multiple organ systems, and progression of clinical signs is often directly related to the quantity eaten. Diagnostic detection of the toxins is rarely an option; rather, diagnosis is based on a history of possible exposure and identification of mushroom species in the stomach contents and environment. Treatments are usually based on clinical signs, as most mushroom toxins are without an antidote. There are exceptions, however, and prompt identification of mushroom species involved is vital whenever possible. Collection of the toxicologic minimum database and gastrointestinal decontamination are important in all cases where mushroom ingestion is suspected.