Intentional intoxication with natural hallucinogenic substances such as hallucinogenic mushrooms continues to be a major problem in the US and Europe, particularly in the harbor complex of northwest Poland (Pomerania). A case is described of Psilocybe intoxication in an 18-year-old man resulting in Wolff-Parkinson-White syndrome, arrhythmia, and myocardial infarction. The indole concentrations of hallucinogenic mushrooms may predict the risk for adverse central nervous system and cardiac toxicity.