Over the past decade, government authorities have worked closely with organizations and professionals in the fields of substance abuse and AIDS prevention to develop a public health policy aimed at preventing health and social problems associated with drug use, particularly HIV and hepatitis infections resulting from needle-sharing among intravenous drug users (IDUs). In practical terms, the 1987 decree authorizing the over-the-counter sale of syringes was followed by the launch of syringe exchange programs (SEPs) and the introduction of prevention kits sold in pharmacies (Stéribox, 1994). At the same time, IDUs’ access to substitution treatments has been greatly facilitated since methadone (March 1995) and Subutex (February 1996) became available by prescription in private practice. In an effort to combat the main health consequences associated with drug use, access to injection equipment should have led to an increase in the number of syringes sold or distributed from 1996 to 1999, whereas the substitution policy should instead have resulted in a decrease in injection and heroin use, reflected in a gradual decline in heroin use and fatal overdoses over the same period. What is the actual situation? The InVS manages an information system (SIAMOIS) that has tracked, since 1996, the sales of syringes and substitution products intended for IDUs across all French pharmacies. Based on a summary of major trends from SIAMOIS data from 1996 to 1999 and the triangulation of these data with socio-health risk indicators related to drug addiction, Volume 1 of a two-part report undoubtedly provides as many answers as it raises new questions, with the aim of improving the relevance and quality of prevention efforts targeting IDUs. The detailed analysis of this monitoring (raw and refined data by region and department) is the focus of this volume, intended in particular for local stakeholders who need objective data to initiate, evaluate, and coordinate harm reduction efforts in their area of activity. (R.A.)