In Europe，Precursor chemicals，or so-called “Drug precursors” are widely，though imprecisely，used for a range of substances which，besides applications in the chemicals industry，are also components of illicit drugs. Traffickers use various means to divert these substances from licit trade，including setting up “front” companies and colluding with precursor producers or traders. These chemicals may also have legitimate uses，necessitating a regime of regulation at the global level to prevent their diversion for illicit use and thereby limiting the supply of illicit drugs. Given the primary purpose of drug precursors，the EU legislator’s response needs to strike a balance between preventing their illicit use and the commercial needs of legitimate operators. In order to avoid regulatory regimes，producers of illicit synthetic drugs have introduced alternative chemicals that are not listed in the precursor regulations. These chemicals，which are normally imported，are converted into drug precursors that are then used for synthetic drug production. Because alternative chemicals are not controlled，they are cheaper than drug precursors and can be traded with little risk of interdiction or heavy penalties. The emergence of these new substances is a serious challenge to the international precursor control system. MDMA，amphetamine and methamphetamine are produced in the European Union in illicit laboratories to satisfy the demands of European consumers，and increasingly to supply consumers in other regions of the world. To produce these illicit drugs，chemical starting materials called drug precursors are needed. BMK，ephedrine and pseudo-ephedrine（used for amphetamine and methamphetamine）and PMK（ecstasy）are among the most sought-after substances of this kind. A set of EU regulations provide an implementing framework for precursor trade within the European Union and between the European Union and the rest of the world.