Illicit drugs are a global problem. More than 200 million people abuse drugs worldwide. The illicit drug problem can be divided into three categories, First, those illicit drugs that are either produced or processed from natural plant products such as opium, heroin, and cocain. Secondly, synthetically produced illicit drugs, such as amphetamine. and thirdly, psychoactive pharmaceutical drugs that become illicit as a result of being diverted from licit uses or purposes. The present study is concerned primarily with the first and, to a lesser extent, the second category. The third category is not considered here. The three major international drug control treaties are mutually supportive and complementary. An important purpose of the first two treaties is to codify internationally applicable control measures in order to ensure the availability of narcotic drugs and psychotropic substances for medical and scientific purposes, and to prevent their diversion into illicit channels. They also include general provisions on illicit trafficking and drug abuse. Single Convention on Narcotic Drugs aims to combat drug abuse by coordinated international action. There are two forms of intervention and control that work together. First, it seeks to limit the possession, use, trade in, distribution, import, export, manufacture and production of drugs exclusively to medical and scientific purposes. Second, it combats drug trafficking through international cooperation to deter and discourage drug traffickers. At present, control is exercised over more than 116 narcotic drugs under this convention. They include mainly natural products such as opium and its derivatives, morphine, codeine and heroin, but also synthetic narcotics such as methadone and pethidine, as well as cannabis and cocaine. Convention on Psychotropic Substances establishes an international control system for psychotropic substances. It responded to the diversification and expansion of the spectrum of drugs of abuse and introduced controls over a number of synthetic drugs according to their abuse potential on the one hand and their therapeutic value on the other. In contrast to illicit traffic in narcotic drugs, which are obtained from illicit production and manufacture, psychotropic substances are often obtained through diversions from legitimate manufacture. These diversions stem mainly from inadequate legislation in a number of manufacturing and exporting countries and the lack of advance information on actual medical and scientific requirements. Millions of dosage units of such unwanted substances have thus been "exported" to countries that had no use for them, and end up being abused worldwide. At present 111 psychotropic substances are controlled by this convention. Most of them are contained in pharmaceutical products acting on the central nervous system. Broadly speaking, these are the hallucinogens, the stimulants and the depressants and some analgesics. Convention against the Illicit Traffic in Narcotic Drugs and Psychotropic Substances provides comprehensive measures against drug trafficking, including provisions against money laundering and the diversion of precursor chemicals. This convention introduced a number of control measures on various substances frequently used in the illicit manufacture of narcotic drugs and psychotropic substances. The article entrusted the Board with the responsibilities of monitoring the implementation by Governments of the control measures over such substances and assessing chemical substances for possible international control. Under the three main international drug control treaties, States have an obligation to communicate their drug control legislation to the United Nations. It is essential for governments and institutions that have made a commitment to social and economic progress to pay greater attention to drug control and integrate drug control efforts into programmes that promote long-term economic development. It could be argued that drug control is a prerequisite for successful economic development, while successful economic development may also be a precondition for sustainable success in drug control. The measures of control that these two Conventions prescribe vary in strictness from one group of drugs to another. For this purpose, drugs are listed in various schedules annexed to the Conventions according to the differences in their dependence-producing properties, their therapeutic value and their risk of abuse. Both WHO and parties are authorized to propose a change to the list of controlled drugs. The United Nations Commission on Narcotic Drugs(CND), a functional Commission of ECOSOC, has the power to determine whether a new drug should be listed, or whether a listed drug should be transferred to another schedule or deleted. In so doing, the Commission must take into account the findings and recommendations of the World Health Organization (WHO). Besides the control of narcotic drugs and psychotropic substances, both of which are dependence-causing substances, international drug control has been extended by the 1988 Convention to 22 chemicals frequently used in the illicit manufacture of narcotic drugs or psychotropic substances. The international system of controlling the licit movement of narcotic drugs under the Single Convention on Narcotic Drugs functions in a generally satisfactory manner, and licitly produced or manufactured drugs usually do not constitute a source for illicit traffic. The fact that the system generally works well is mainly due to the estimates system that covers all countries whether or not parties to the Convention. Countries are under an obligation not to exceed the mounts of the estimates confirmed or established by the Board.