UNLABELLED: Background Rates of sexually transmissible infections (STIs) have increased over recent years among gay men and other men who have sex with men (MSM) in England and Wales. HIV diagnoses remain high in this group and men with diagnosed HIV are disproportionally affected by STIs. MSM are therefore a priority for health promotion efforts to reduce STIs. Understanding awareness of and attitudes towards STIs is essential in developing health promotion interventions to reduce prevalence. METHODS: Eight focus group discussions (FGDs) with a total of 61 MSM in four English cities included a ranking exercise to gauge how 'scary' participants thought 11 STIs are. The exercise sought insights into participants' awareness of, knowledge about and attitudes towards STIs and blood-borne viruses (BBVs). FGDs were audio-recorded, transcribed and data analysed thematically. RESULTS: All groups ranked HIV and Hepatitis C virus (HCV) as the scariest infections, and the majority ranked syphilis and herpes as highly scary. Scabies was ranked as the least scary by most groups. Rankings were dependent on how well informed participants felt about an infection, its transmission mechanisms, health affect and the availability of vaccines and treatment. Personal experience or that of friends influenced perceptions of particular infections, as did their prevalence, treatment options, visibility of symptoms and whether an STI could be cleared from the body. CONCLUSIONS: The study findings suggest that, although some MSM are well informed, there is widespread lack of knowledge about the prevalence, modes of transmission, health implications and treatment regimens of particular STIs.