The defining scholarly publication on the past and current state of research with psychotropic plant substances for medicinal, therapeutic, and spiritual uses. Certain plants have long been known to contain healing properties and used to treat everything from depression and addiction, to aiding in on one’s own spiritual well-being for hundreds of years. Can Western medicine find new cures for human ailments by tapping into indigenous plant wisdom? And why the particular interest in the plants with psychoactive properties? These two conference volume proceedings provide an abundance of answers.