The human immunodeficiency virus (HIV) epidemic among injecting drug users (IDUs) shows different developments in different parts of the European region. In the countries of the European Union (EU) and the European Free Trade Association (EFTA), the rates of reported newly diagnosed cases of HIV infection in IDUs are mostly at stable and low levels or in decline. In contrast, those rates increased in 2007 in many of the other (eastern) countries in the World Health Organization (WHO) European Region, suggesting that the HIV epidemic among IDUs in Europe is still growing. In countries or regions where indicators of HIV incidence show upward trends, existing prevention measures may be insufficient and in need of strengthening. In the EU/EFTA region the larger availability of harm reduction measures such as opioid substitution treatment and needle and syringe programmes may have played a key role in containing the epidemic among IDUs.