The peyotl is a cactus which grows in certain parts of Mexico and is used by various groups or tribes of Indians in Mexico and the United States for different purposes, including cult purposes. Its principal alkaloid, mescaline, is of some importance in psycho-pharmacology. Peyotl is not one of the drugs placed under international control by virtue of the international instruments relating to narcotic drugs. It was discussed at the twenty-first session of the League of Nations Advisory Committee on Traffic in Opium and Other Dangerous Drugs. The information in this article has been compiled from the literature published on the subject.