This book, authored by experienced researchers in the hallucinogenic drug field, is intended to fill the gap created by most previously published work, which tends to be either highly technical or emotional and partisan. The authors range from ardent proponents to skeptics, but they share a commitment to scientific evidence and the clear explication of it. Of the 9 chapters, only one is devoted exclusively to a discussion of the psychological state produced by psychedelic agents, perhaps reflecting the presumed sophistication of the reading audience. Two chapters relate studies of LSD in the treatment of alcoholism. In another chapter an early enthusiast of LSD treatment for many conditions, now is circumspect about its therapeutic efficacy. Adverse reactions to LSD are the sole focus of two authors, and the chapters on therapeutic applications also tabulate untoward effects. In reading through the discussions of chromosome damage and embryonic malformations, one is struck by the fact that now, almost two yr since these were first noted, their relevance to human drug takers is still unclear. The verified dangers of psychedelic drug use are psychological in nature, including prolonged psychotic episodes and 'flash backs'. It might be useful to attempt to define 'hallucinogenic' drugs. A number of terms have been used interchangeably to designate these psychoactive agents, including 'hallucinogen', 'psychedelic', 'psychotomimetic', 'psychodysleptic', and 'psychosomimetic'. This class of drugs embraces a variety of chemicals which share the ability to produce a unique and specific assortment of subjective changes in human subjects. Drugs of this type include d lysergic acid diethylamide (LSD 25), dimethyltryptamine (DMT), psilocybin, mescaline and a group of compounds chemically related to mescaline and amphetamine of which the two best known examples are 'STP' (DOM) (2,5 dimethoxy 4 methylamphetamine) and MDA (3,4 methylenedioxyamphetamine). Their hallmark is the evocation of marked alterations in self awareness. STASH is a student run organization devoted to the dissemination of valid information about psychoactive drugs.