Men who inject drugs (IDUs) and have sex with men (MSM) have a four-fold higher risk of HIV than those who only have sex with women (MSW), a national survey has found. Prevalence of hepatitis C (HCV) was also a third higher in the former group. IDUs in England, Wales and Northern Ireland have been recruited into a voluntary unlinked anonymous cross-sectional survey annually since 1990. The survey includes an oral swab for HIV and HCV and a questionnaire on demographics and risk behaviours. A total of 8,671 male IDUs who reported having had sex and injecting drug use in the previous 12 months took part in the survey for the first time between 1998 and 2007. Median age was 29 and median period of injecting drug use seven years.