The purpose of this thesis is to analyze changes over time in the interactions of street-involved youth with their risk environments and to investigate how their integration into local, provincial, and federal systems and services impacts their lives, health, and substance use. This thesis employs a sequential explanatory mixed methods design and uses closed and open-ended questions collected over five waves of interviews during the longitudinal study Risky Business? Experiences of Street-Involved Youth. Quantitative (n = 50) methods of analysis include descriptive statistics and bivariate comparisons complemented by a qualitative (n = 15) thematic analysis comprised of open-ended interview questions. The risk environment framework proposed by Tim Rhodes is used to highlight structural and systemic forces informing the lives of street-involved youth, allowing for an analysis on three levels of influence (micro, meso, macro) and four types of environment (economic, physical, social, policy). Results indicate that comparatively high substance use and harms of substance use among street-involved youth decrease as they become integrated into local, provincial, and federal systems and services. Intersecting demographic and structural factors correspond with higher substance use for male youth and youth who had been involved with the foster care system during their life. Given the diversity of backgrounds and risk environment experiences, street-involved youth expressed diverse opinions and perspectives regarding the effectiveness of healthcare, harm reduction, and outreach services. Policy recommendations and suggestions for future research are suggested, with the aim of developing safer environments and environment interventions for street-involved youth that reduce substance use-related harms. / Graduate