This glossary arises out of research interests in the 19th and 20th century in the history of drugs, including the contemporary history of drug policy. It is necessarily brief, and British and American focused; it is also concentrated on narcotic drugs rather than alcohol and tobacco. However, the comments take on board the recent discussions of convergence across the substances, and also the spread of the concept of addiction to tobacco in recent years. The bibliography is also limited to specific interests.