Mephedrone is a synthetic psychostimulant derived from cathinone belonging to the family of phenylethylamines. Sold on the Internet, it has recently emerged in France in recreational settings, and is mostly consumed by young people from the gay community and festive environment. Identified in 2008 by the European Monitoring Centre for Drugs and Drug Addiction as a new drug on the market, the use of mephedrone has attracted media attention following the suspicious deaths of two young adults in Sweden and in England. Its legal aspect, ease of getting it on the Internet and cheap price coupled and an alternative-seeking to other psychostimulants make mephedrone a prime target for these populations and a source of abuse, with psychiatric and somatic complications. There is no curative pharmacological treatment approved by health authorities.