This is one of the first qualitative event-based studies to understand the various mechanisms through which multiple factors influence condom use decision making among homeless youth. Event-level interviews that explore characteristics of the environment surrounding sexual events were conducted with 29 youth who were asked to describe two recent sexual encounters. In thematic analyses of data across events, reasons that youth gave for engaging in unprotected sex included the expectation of having sex and use of alternative methods of protection against pregnancy. Other nonevent factors that influenced condom use decision making were related to attributes of the partnership (e.g., testing, trust and love, and assessments of risk) and attributes of the youth (e.g., perceptions of diseases, concerns over pregnancy, and discomfort using condoms). Additional event analyses conducted within the same individuals found that decision making was influenced by multiple interacting factors, with different pathways operating for event and nonevent factors. Future interventions should consider taking a multilevel and individualized approach that focuses on event-based determinants of risky sex in this population.