Relationship status is an important factor associated with condomless anal intercourse CAI amongst men who have sex with men MSM. Our results speak to the need to consider segmented and tailored public health and health promotion initiatives for MSM with differing CAI behaviours and relationship profiles. In order to develop and implement community-level risk-reduction initiatives targeting MSM, it is necessary to examine not only key sexual behaviours amongst different MSM sub populations, but to also understand and consider the context in which they occur; relationships are one such context. Nevertheless, examining explanatory factors related to differences in CAI between MSM in steady and casual relationships can be important in order to interrogate segmented public health and health promotion initiatives for MSM with differing sexual behaviour and relationship profiles. Consequently, in this present analysis we utilize data from the EU-funded Sialon II study which was a large multi-centre biological and behavioural cross-sectional survey of MSM in community settings carried out across 13 European cities.