We enrolled 166 gay and bisexual men who tested HIV-negative at a community sexual health clinic in Vancouver, British Columbia, into a year-long mixed-methods study. A subsample of participants who reported recent condomless anal sex (n = 33) were purposively recruited into an embedded qualitative study and completed two in-depth qualitative interviews. Analysis of baseline interviews elicited three narratives relevant to men's use of context- or relationally-dependent HIV-risk management strategies: (1) seroadaptive behaviours such as partner testing and negotiated safety agreements used with primary sexual partners, (2) serosorting and seroguessing when having sex with new partners and first-time hookups and (3) seroadaptive behaviours, including one or more of seropositioning/strategic positioning, condom serosorting and viral load sorting, used by participants who knowingly had sex with a serodiscordant partner. Within men's talk about sex, we found complex and frequently biomedically-informed rationale for seroadaptation in men's decisions to have what they understood to be various forms of safe or protected condomless anal sex. Our findings support the need for gay men's research and health promotion to meaningfully account for the multiple rationalities and seroadaptive strategies used for having condomless sex in order to be relevant to gay men's everyday sexual decision-making.