BACKGROUND: Men who have sex with men (MSM) are at increased risk of HIV infection in both high- and low-income settings. Mass media campaigns have been used as a means of communicating HIV health promotion messages to large audiences of MSM. There is no consensus on which designs are most appropriate to evaluate the process and outcomes of such interventions. METHODS: An exploratory review was conducted to assess research examining awareness, acceptability, effects on HIV testing, disclosure and sexual risk, and cost-effectiveness of HIV mass media campaigns targeting MSM. We searched for quantitative and qualitative studies published between 1990 and May 2011 via the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Psych Info, ISI Web of Science, OpenGrey and COPAC, and contacting experts. No exclusions were made on the basis of study design or methods because our primary aim was to map evidence. We appraised study quality and present a narrative synthesis of findings. RESULTS: Sixteen reports from 12 studies were included. All were from high-income countries and most examined multi-media interventions. Half of the studies were single cross-sectional surveys. Three repeat cross-sectional studies collected data pre and post the campaign launch. The remaining three studies monitored routine data. Three studies included a nested qualitative component. Campaign coverage was the most commonly reported outcome (9 studies). Imagery, tone of language, content and relevance were identified in the qualitative research as factors influencing campaign acceptability. HIV testing rates (or intention to test) were reported by five studies. Two studies reported that testing rates were higher among men who had seen the campaigns compared to men who had not, but this may reflect confounding. Findings were less consistent regarding reductions in sexual risk behaviours (4 studies). None of the studies examined cost-effectiveness. CONCLUSIONS: Campaigns aim to provide MSM with information to help prevent transmission of HIV and to address increasing motivation and changing norms towards precautionary behaviours. However, the limitations of mass media in imparting skills in effecting behaviour change should be recognised, and campaigns supplemented by additional components may be better-suited to achieving these goals.