Objectives Swingers, that is, members of a heterosexual couple who, as a couple, had sex with other couples and/or singles within the swinger’s subculture, are a hidden population with substantial rates of sexually transmitted infections (STIs) and high-risk sexual behaviour. Information on swingers’ self-identification to be a swinger, their risk perception and attitudes about STI testing and safe sex will help to reveal swingers who are hidden while in care, to address them with targeted strategies.

Methods We used data from a convenience sample of 289 swingers from our Dutch STI clinic patient registry between 2009 and 2012 (median age 45 years; 49% women; STI positivity 13%, no condom in vaginal sex: 57%). Participants filled in a self-administered questionnaire on sexual behaviour and answered statements about self-identification, risk perception and attitudes about STI testing and safe sex.

Results Of all participating registered swingers, 56% self-identified as a swinger. Safe sex was reportedly deemed important (77%). Overall, 72%, 62% and 56% reported that STI testing, partner notification and condom use is the norm in the swinger community. The latter was reported more often by self-identified swingers compared with non–self-identified swingers. Self-identified swingers further swinged more often, had more partners and more often swinged at home parties than non–self-identified swingers.

Conclusions About half of STI clinic attending swingers whose sexual behaviour agrees with the definition of swinging are neutral/do not identify themselves to be a swinger. As many STI clinics internationally not specifically ask clients about their swinging behaviour, swingers may be a missed target population in care. Implementation of routine questions addressing behaviour (thus not only asking whether someone is a swinger) in STI clinics is feasible and facilitated by swingers’ positive norm towards STI prevention and testing. Implementing routine swinger questions contribute to effective STI services including appropriate testing, counselling and partner notification.