Hallucinogens are mood-altering drugs that cause the user to experience hallucinations, dissociation from reality, or delirium. Hallucinogens such as psilocybin (mushrooms) and mescaline (peyote) are naturally occurring, while LSD, MDMA, PCP, and ketamine are synthetic substances. Abuse of hallucinogens can cause memory impairment, anxiety attacks, flashbacks, nausea, and vomiting. High doses of hallucinogens like PCP can cause convulsions, coma, and death. Hallucinogens provides important information on the nature and chemistry of these drugs, their effects, abuse, and related social and legal issues. Chapters include: Overview History of Hallucinogens The Science of Hallucinogens Hallucinogens: Use and Abuse Treatment for Hallucinogen Abuse Hallucinogens and the Law Future Trends.