Objectives Increasing HIV testing among men who have sex with men (MSM) is a major policy goal in the UK. Social marketing is a common intervention to increase testing uptake. We used an online panel of MSM to examine rates of HIV testing behaviour and the impact of a social marketing intervention on them.

Method MSM in England were recruited to a longitudinal internet panel through community websites and a previous survey. Following an enrolment survey, respondents were invited to self-complete 13 surveys at monthly intervals throughout 2011. A unique alphanumeric code linked surveys for individuals. Rates of HIV testing were compared relative to prompted recognition of a multi-part media campaign aiming to normalise HIV testing.

Results Of 3386 unique enrolments, 2047 respondents were included in the analysis, between them submitting 15 353 monthly surveys (equivalent to 1279 years of follow-up), and recording 1517 HIV tests taken, giving an annual rate of tests per participant of 1.19 (95% CI 1.13 to 1.25). Tests were highly clustered in individuals (61% reported no test during the study). Testing rates were higher in London, single men and those aged 25–34 years. Only 7.6% recognised the intervention when prompted. After controlling for sociodemographic characteristics and exposure to other health promotion campaigns, intervention recognition was not associated with increased likelihood of testing. Higher rates of testing were strongly associated with higher number of casual sexual partners and how recently men had HIV tested before study enrolment.

Conclusions This social marketing intervention was not associated with increased rates of HIV testing. More effective promotion of HIV testing is needed among MSM in England to reduce the average duration of undiagnosed infection.