Theoretical models of sexual risk-taking have traditionally focused on personal characteristics, but conceptual approaches emphasizing the social and situational context have also been proposed. This study examined the impact of characteristics of the person and of the sexual encounter on unprotected anal intercourse (UAI) among 482 immigrant Latino MSM. Analyses included logistic regression and hierarchical linear modeling. The personal characteristic of self-efficacy for safer sex was negatively associated with UAI over the previous three months, at the most recent encounter, and over multiple encounters reported by each participant. In addition, a cross-level interaction of self-efficacy at the person-level and sexual desire at the encounter-level showed that increased sexual desire was associated with greater likelihood of UAI for those with low self-efficacy, but not those with high self-efficacy. Likelihood of UAI was also linked to the situational characteristics of closeness to the partner, seroconcordance, and concern about STIs in the encounter.