Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) and psilocin are chemical compounds obtained from certain types of dried or fresh hallucinogenic mushrooms found in Mexico, South America and the southern and northwest regions of the United States. Psilocybin is classified as an indole-alkylamine (tryptamine). These compounds have similar structure to lysergic acid diethylamide (LSD), and are abused for their hallucinogenic and euphoric effects to produce a "trip". Hallucinogenic (psychedelic) effects are probably due to action on central nervous system serotonin (5-HT) receptors.
There are over 180 species of mushrooms that contain the chemicals psilocybin or psilocin. Like the peyote (mescaline), hallucinogenic mushrooms have been used in native or religious rites for centuries. Both psilocybin and psilocin can also be produced synthetically in the lab. There have been reports that psilocybin bought on the streets can actually be other species of mushrooms laced with LSD.