This is the only identification guide exclusively devoted to the world's psilocybin-containing mushrooms. Detailed descriptions and colour photographs for over one hundred species are provided, as well as an exploration of their long-standing (and often religious) use by ancient peoples and their continued signifigance to modern-day culture. Some of these species included have just been discovered in the past year or two, and still others have never before been photographed in their natural habitats.