Background : Structural and environmental factors are that influence risk behaviors for HIV and tuberculosis (TB) outcomes are increasingly relevant in determining risk. The impact of the residential environment, including the social and physical living space, may be particularly influential in HIV or TB risk. Aims : Our main objectives in this study were to (1) describe and characterize housing types and changes in housing over time among female sex workers that inject drugs (FSW-IDU) living along the Northern Mexico border to define an appropriate housing stability measure (2) determine the association of the housing environment (i.e. housing stability) with HIV/STI sexual risk behaviors (i.e. unprotected sex by partner type) among FSW-IDU (3) determine the impact of drug use in the social living environment (passive smoking) on latent TB infection (LTBI) in the US civilian non-institutionalized population. Methods : Chapters 2 and 3 used quantitative housing data from the longitudinal Mujer Mas Segura dataset of FSW-IDU in Ciudad Juarez and Tijuana. Chapter 2 uses data on housing types and longitudinal trends in housing to consider what characterizes housing stability among FSW-IDU. Chapter 3 describes the association between housing stability measures and unprotected sex by client type among FSW-IDU. Chapter 4 used available data from the US National Health and Nutrition Examination (NHANES) survey to describe the association between passive smoking and LTBI. Results : Chapter 2 found that FSW-IDU frequently moved; only 11.5% were in the same housing type across all visits (18 months). Less than a quarter of FSW-IDU lived in stable housing and receptive needle sharing and unprotected sex where higher among those with greater housing instability. Chapter 3 found that improving housing categories was associated with less unprotected sex in bivariate associations, but was not significantly associated after adjustment with individual and social level covariates. Chapter 4 found a marginally significant association between passive smoking and LTBI in the general adult population after adjustment for confounders. Among the foreignborn in the US, passive smoking was significantly associated with LTBI. Conclusion : Both the residential environment and individual risk factors are important when determining risk of HIV and TB.