The term hallucinogens refers to a diverse group of drugs, natural or synthetic, that induce an alteration in perception, thought, emotion and consciousness. Hallucinogens have been investigated as potential therapeutic agents in treating several disorders including depression, obsessive-compulsive disorder, alcohol dependence and opiates addiction. A moderate dose of LSD will produce a profound alteration in mood, sensation and consciousness, intensified sensory experiences and perceptual distortions. MDMA (Ecstasy) users experiences euphoric feelings, and feelings of empathy, relaxation and meaningfulness. Tactile sensations are enhanced for some users, making physical contact with others more pleasurable. GHB is consumed by teenagers and young adults in various recreational and club settings, with users enjoying an alcohol-like high with potent positive sexual effects. GHB causes intoxication resembling alcohol or ketamine intoxication and can lead to respiratory depression and death, especially when combined with alcohol. Ketamine is an anaesthetic that inhibits painful sensations and is used in human anaesthesia and veterinary medicine. Psilocybin’s sought after effects are similar to LSD, but the hallucinogenic trip is often milder and shorter. There is evidence to suggest that certain hallucinogens can be addictive (PCP) and that tolerance can be developed for certain hallucinogens (LSD); some hallucinogens also produce tolerance to other similar drugs.