black market occasionally demonstrate the presence of 
psilocybin; Oregon, Washington, and British Columbia have 
been the sources of much of the material giving positive tests 
(8). 
Between 1973 and 1976 I made a number of visits to the 
Pacific Northwest in order to find and identify psychoactive 
mushrooms and learn something of their use. I had the good 
fortune to find four species containing psilocybin and to meet 
and interview a number of users of these species. I also talked 
with users of species in the genus Amanita, commonly re- 
garded as the most dangerous group of all mushrooms. In this 
paper, I shall report observations and experiences with these 
psychoactive fungi and their users (9). 
II. 
Psilocybin is a strong hallucinogen that occurs in species of 
Psilocybe, Stropharia, Conocybe, and Panaeolus , and, so far 
as known, nowhere else in the Plant Kingdom. It may occur in 
combination with psilocin, a closely related compound with 
equivalent effects. Psilocybin is the phosphate ester of psilocin 
and the only known natural indole with a phosphoric acid 
radical. Psilocin is 1.4 times as potent as psilocybin, and, 
presumably, when psilocybin is ingested, it is first converted to 
psilocin in the body. Many texts give the mean oral dose of 
psilocybin as 4 to 8 mg., equivalent to about 2 gm. of the dried 
mushroom Psilocybe mexicana Heim (10). I think this figure is 
low, since experienced users of hallucinogens report 10-20 mg. 
to be a moderate dose. 
In doses of 10-20 mg., psilocybin produces a distinctive 
intoxication marked by visual hallucinations. In certain set- 
tings, with proper expectation, it may induce mystical or reli- 
gious feelings (11). Its effects wear off in four to six hours, and 
even high doses commonly leave no after-effects. 
In the North American drug subculture, psilocybin is held in 
high esteem. Its duration of action, only half as long as that of 
LSD and mescaline, recommends it for convenience. Its power 
to induce visions is great. It is gentler on the body than other 
hallucinogens. And it comes from mushrooms, which, for 
many persons, are fascinating symbols of the unconscious or 
‘‘night’’ side of human experience (12). For all these reasons, 
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