Aim: To describe social characteristics seen among socially excluded drug users in 10 cities from 9 European countries, and identify which social exclusion indicators (i.e. housing, employment, education) are most closely linked to intravenous drug use. Design: Cross-sectional survey. Setting: Interviews were held in social services centers, town halls, streets, squares and other usual meeting points of the target population. Participants: The sample comprises 1,879 participants who have used heroin and/or cocaine and certain derivatives (92.3%) over the last year. Males accounted for 69.7% of the sample, and the mean age was 30.19 years. Participants were recruited in 10 cities: Seville and Granada, Spain; Cologne, Germany; Vienna, Austria; Brussels, Belgium; Athens, Greece; Dublin, Ireland; London, England; Lisbon, Portugal, and Perugia, Italy. Measurements: Structured face-to-face questionnaire, conducted by privileged access interviewers. Results: Cannabis, heroin and cocaine are the most widely used substances. In the total sample, 60.2% injected drugs during the last year, 45.9% reported having hepatitis C; 54.9% have been in prison; 14.2% are homeless; 11.3% have a regular job, and 35.2% are involved in illegal activities. Hierarchical logistic regression analysis (injectors and non-injectors) showed that older participants have a greater likelihood of injecting than younger ones. Social exclusion variables associated with intravenous drug use are incarceration, homelessness, irregular employment, and delinquency. Participants who abandoned or were expelled from a drug treatment program are at greater risk of injecting drugs than participants who have never had treatment, are currently in treatment or have been released. Conclusion: Personal, social, and economic conditions are all linked in a process of social exclusion that compounds problem drug misuse. Given the findings of this study, we believe that there is a clear need for specific programs targeting specific groups, i.e., distinct strategies must be set in place, in line with the profile and needs of the patient in each context.