Abstract: Methods for impurity profiling of heroin and cocaine1982 to coordinate research on the physical and chemical characteristics of heroin for the purpose of tracing origin and movement in the illicit traffic [2].In 1992, a consultative meeting on chemical characterization and impurity profiling of drug seizures was held in Vienna; that meeting expanded coverage beyond heroin to include cocaine and synthetic drugs and, in particular, amphetamine [3].At its thirty-ninth session, in 1996, the Commission on Narcotic Drugs recognized the need for a cohesive international strategy in the field of drug characterization and impurity profiling.In so doing the Commission requested the Executive Director of the United Nations International Drug Control Programme (now called UNODC) to develop standard protocols and methods for the profiling/ signature analysis of key narcotic drugs and psychotropic substances [4].The objectives of the Office in this area are to develop guidelines for characterization and impurity profiling of key narcotic drugs and psychotropic substances and to make the guidelines available to national forensic laboratories with the aim of providing them with a scientific tool to support law enforcement work for both evidential and strategic intelligence purposes.At the same time, the UNODC reference services, which include the provision of training, reference samples, material and scientific literature, were expanded to include specific aspects of drug characterization and impurity profiling as well.In this context and in view of the focus of the General Assembly at its twentieth special session on, inter alia, the need for enhanced measures to counter illicit manufacture of and trafficking in drugs, it was considered timely to review profiling methods for heroin and cocaine, along with the broader concepts of drug characterization and impurity profiling of both plant-based and synthetic drugs.To this end, the Laboratory and Scientific Section of UNODC convened a Consultative Meeting on Recommended Methods for the Impurity Profiling of Heroin and Cocaine, in cooperation with the Government of Australia, in Sydney, Australia, in November 1999. B. Purpose of the manualThe present manual, prepared by the Laboratory and Scientific Section of UNODC, reflects the discussions and conclusions of the Consultative Meeting held in Sydney.It is aimed at providing practical guidance to national drug testing laboratories that want to embark on heroin and/or cocaine profiling activities.The broader aspects of how drug characterization and impurity profiling can be used effectively as a scientific tool to support law enforcement operational investigative work can be found in a separate manual entitled Drug Characterization/ Impurity Profiling: Background and Concepts [5], which was endorsed by the participants at the Consultative Meeting.Both manuals form part of a series of publications dealing with the identification and analysis of various groups of drugs under international control.Specifically, the present manual complements United Nations manuals on recommended methods for testing opium, morphine and heroin [6] and on cocaine [7].These and other manuals in the series, including those the United Nations manual entitled Drug Characterization/Impurity Profiling: Background and Concepts [5].The Laboratory and Scientific Section would welcome observations on the contents and usefulness of the present manual.