In response to a notified increase in HIV cases among injecting drug users (IDU) in Greece and Romania, the European Commission asked the European Centre for Disease Prevention and Control (ECDC) and the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) in November 2011 to conduct a rapid inquiry among their network of HIV surveillance- and drug focal points to investigate whether such increases had occurred in other countries. The assessment showed that while most European countries reported no changes in the rate of newly diagnosed cases of HIV or HIV prevalence in IDU in 2011, increases were documented in six countries. Indicators of injecting risk and prevention coverage show a potential risk for increased HIV transmission and future outbreaks in several countries.