The research topic of barebacking emerged in the mid-1990s. Since then, a multitude of studies, largely from the United States, have produced invaluable knowledge of factors that help explain the behaviour among men who have sex with men (MSM), and that may contribute to HIV risk reduction programming and advice to counsellors working with barebackers. Given the scant empirical research about barebacking among European MSM, we conducted a survey among 3,634 MSM recruited through a web community in Nordic countries. The objectives of the study were twofold: to describe the sexual activities associated with barebacking behaviour at last sexual encounter, and to evaluate the relationship of barebacking with relevant variables. Men who reported barebacking (n=356) and men who did not (n=3,278) were compared. On the basis of the results of the analyses, the socio-sexual profile of barebackers drawn was one that is at increased risk of acquiring human immunodeficiency virus (HIV) and other sexually transmitted infections due to their sexual practices, particularly unprotected anal intercourse, but also group sex and rimming. In a multivariate logistic regression analysis, the likelihood of engaging in barebacking was higher for MSM who reported more frequent HIV testing (odds ratio (OR)=5.16), a higher number of female sex partners (OR=16.80), using gay cruising places (OR=1.51) and gay chat rooms (OR=2.11).