Abstract: Key findings: HIV: The prevalence of HIV infection among injecting drug users (IDUs) in England and Wales has increased in recent years. Overall, around one in 50 IDUs are now infected, which is still low compared to many other countries. The prevalence remains elevated among IDUs in London with around one in 25 HIV infected. The recent increase in HIV prevalence has been greatest elsewhere in England and Wales, where the prevalence has risen from around one in 400 in 2003 to about one in 65 in 2005. Hepatitis C: Overall, approaching one in two IDUs in the UK have been infected with hepatitis C, which is also low compared to many other countries. However, there are marked regional variations in hepatitis C prevalence within the UK, with the low prevalences found in some areas suggesting that hepatitis C infection is not an inevitable consequence of injecting drug use. Surveillance and research data also indicate that the overall prevalence of hepatitis C infection among IDUs has probably increased in recent years and that levels of hepatitis C transmission remain elevated. Voluntary confidential diagnostic testing: Uptake of testing for hepatitis C among IDUs in contact with drug services has increased in recent years. It is estimated, however, that almost half of those IDUs with hepatitis C in contact with these services still remain unaware of their infection. There will also be substantial numbers of current and former IDUs who are not in contact with services who will be unaware they have hepatitis C. Whilst most IDUs in contact with services report having had a test for HIV at some point, less than half of those with HIV are aware of their infection. There is therefore a need to improve the provision of voluntary confidential testing services for both hepatitis C and HIV. Vaccination: The proportion of IDUs reporting uptake of hepatitis B vaccination has increased markedly in recent years, with the prison vaccination programmes being a major factor in this increase. However, the transmission of hepatitis B continues among IDUs. There is a particular need to improve the provision of vaccinations to IDUs through needle exchange services, including the provision of the vaccines against hepatitis A and tetanus as well as that against hepatitis B. In England, the National Treatment Agency for Substance Misuse (NTA) is developing performance monitoring for the provision of vaccination by services for drug users. Bacterial infections: The ongoing occurrence of wound botulism cases indicates that the environmental contamination of heroin with bacterial spores remains a problem. There are also continuing problems with injecting site infections associated with methicillin resistant Staphylococcus aureus and severe group A streptococcal infection. Behaviours: Levels of reported needle and syringe sharing increased in the late 1990s, and since then have remained elevated with over a quarter of IDUs reporting sharing in the previous month. The sharing of other injecting equipment is more common. There are also indications that injecting into the groin (femoral vein) may be becoming more common. It is also apparent that there are a variety of individual and environmental factors that may affect injecting behaviour and hygiene, and that the effects on risk of factors such as homelessness, the injecting environment, and drugs injected need further investigation. In particular the role of crack-cocaine use, which has become more widespread, is a cause for concern.