In an effort to make knowledge available about how treatment systems for drug users are organized in different countries, and to facilitate bi- and multilateral co-operation and research, this publication presents an overview of the treatment systems of 22 of the 35 Pompidou Group member countries. In most of Europe, the focus of drug treatment in the 1980s and 1990s was on heroin and the introduction of substitution treatment. However, a shift to cater for polydrug use is now taking place across Europe. The diversity of treatment systems reflects the complexity of the local legal, political, economic and cultural context of drug problems. This source of good practices for making treatment accessible and available will be useful not only for policy makers and practitioners, but also for user groups, researchers and the wider public as well.