Epidemics of HIV in men who have sex with men (MSM) were first recognised in the early 1980s. Since the introduction of antiretroviral treatment (ART) in the mid-1990s incidence of HIV has not, despite expectations, reduced significantly in many countries. Indeed, the numbers of new diagnoses has increased in some European countries, the USA and Australia. In the UK, for example, over 3000 MSM were diagnosed with HIV in 2010, the highest number since the beginning of the epidemic. As a consequence, the prevalence of HIV is increasing and, for gay communities, a growing number of men are now living with HIV.

Although incidence of sexually transmitted infections (STIs) in MSM fell dramatically in the early years of AIDS, post-ART we have seen a return in some jurisdictions to pre-AIDS incident STIs, and the emergence of new sexually transmitted pathogens.

This paper will focus on behavioural and epidemiological research in the era of ART, with particular reference to the continuing transmission of HIV. It will review current risk factors for HIV infection in negative MSM, sexual risk behaviour and risk reduction interventions among HIV positive MSM, and the emergence and re-emergence of new and established STIs. It will conclude with current challenges to the prevention of HIV and STIs in MSM, and prospects for the future.