Background : Along the US-Mexico border persons who inject drugs (PWID) with a history of deportation from the US are at increased risk for HIV as compared to non-deported PWID. However, drivers and factors contributing to this elevated HIV risk among deported PWID are poorly understood. Aims : The aims of this dissertation were to: (1) to critically review evidence linking deportation and HIV risk in Mexico; (2) to identify the relationship between deportation and recent (i.e., past 6 months) police victimization experiences (e.g., physical violence, extortion) among PWID in Tijuana, Mexico; and (3) to describe the prevalence and correlates of depressive symptoms among deported PWID in Tijuana, Mexico. Methods : In Chapter 2, a critical review of evidence linking HIV risk and deportation was conducted using existing peer- reviewed research with deported migrants in Mexico. Chapter 3 and 4 draws from questionnaires collected among PWID (n = 733) participating in a longitudinal prospective cohort study in Tijuana. Chapter 3 examines the baseline questionnaires of 733 PWID. Chapter 4 draws on data collected among a subset sample of PWID with a history of deportation (n = 132). Results : Chapter 2 found that deported migrants in Mexico commonly display a higher prevalence of HIV risk behaviors and HIV infection, especially among males and PWID. Various environmental influences that migrants experience post-deportation that may elevate their risk for acquiring HIV infection are discussed. Chapter 3 found that 56% of PWID had experienced police victimization in the past 6-months; differential experiences with police between deported and non-deported PWID were documented. Factors related to being a migrant and a drug user were independently associated with recent police victimization. Chapter 4 found that 45% of PWID reported current symptoms of depression, which was associated with having been initially detained in the US for a crime-related reason before being deported and perceiving needing help with current drug use. Conclusion : HIV vulnerability among migrants who inject drugs is closely linked to their social and physical experience with their receiving environments post-deportation. Structural interventions targeting various social and structural environmental factors are warranted to reduce risks associated with HIV infection