In the context of excessive use of natural or synthetic psychoactive substances, with stimulating, psychedelic and hallucinogenic effects, an increase, if not a recurrence, in consumption of Psilocybe semilanceata has been observed in France over some fifteen years. Psilocybin and psilocin are the active compounds, responsible for the hallucinogenic effects and are a part of the substance group, derived from tryptamine and characterized by an indole nucleus. We report a clinical case observed in an emergency unit and review the historical, epidemiological and pharmacological data now available for these intoxications. Of particular interests in hallucinogenic mushroom abuse are: increased consumption in the context of youth cultural and entertainment movements; possible difficulties in the diagnosis in emergency conditions; possibility of severe and fatal complications.