Background: Drug-related infectious diseases are among the major health consequences of drug use, and any existing drug-related infection may predispose injecting drug users (IDUs) to other infections. Methods: We assessed among IDUs in Budapest, Hungary the prevalence of and vulnerability to selected drug-related infections and co-infections. The sample consisted of 186 participants recruited between October 2005 and December 2006. Results: We found 0% HIV, 37% HCV, 24% HAV, and 14% past HBV infection. Infections with Herpes 1 or 2, tuberculosis, Chlamydia, syphilis, and gonorrhoea were 79%, 12%, 7%, 4%, and 0%, respectively. Co-infection with HAV/HCV was 12%, HBV/HCV 9%, HAV/HBV 7%, and HAV/HBV/HCV 4%. Those over age 30, the ethnic Roma, and the homeless were more likely to have any hepatitis and a higher number of drug-related infections. Amphetamine injectors were more likely to have a higher number of drug-related infections and those who travelled within Hungary were more likely to have any STI. However, those who worked at least part time and those who were in treatment were less likely to have drug-related infections. Conclusions: These results highlight the need of interventions in Hungary to reach and focus on marginalized (Roma or homeless) IDUs and address not only injecting and sex risk, but also hygienic living and injecting conditions. Furthermore, structural interventions to increase social integration (working or being in treatment) may improve welfare and decrease drug use and infection risk tied to drug use/injection among disadvantaged, marginalized, mostly minority populations.