Abstract: In recent decades, the overall level of illicit drug use in Europe has risen dramatically, and with it the number of deaths among the drug-using population, in particular among problem drug users. In the 21st century, a considerable share of premature or avoidable mortality among young adults can be attributed to illicit drug overdose, which accounts for an estimated 4% of deaths among those aged 15–39 in Europe (1). These deaths are often related to injecting drug use and, in most cases, involve a combination of substances (Best et al., 2000), but they represent only part of mortality among drug users (2). In addition, a substantial number of deaths are indirectly related to drug use, such as those from HIV/AIDS related to injecting drug use, accidents, violence and suicides. The high levels of mortality among drug users are a serious cause for concern both at the individual and the societal level. The number of problem opioid users in Europe is cautiously estimated at about 1.3 million (3), and it is among these opioid users, particularly injectors, that we find the greatest share of morbidity and mortality related to illicit drug use in Europe. Heroin is the drug most often associated with overdose, although other drugs and alcohol are commonly present. Overdose represents a major cause of avoidable death associated with illicit drug use, and from 1990 to 2010, between 6 500 and 8 500 overdose deaths have