Drugs are an increasingly salient concern in prisons worldwide. Approximately one-third of people use drugs while in prison, which is associated with a confluence of adverse outcomes. In contrast to extensive epidemiological research, surprisingly little is known about what factors may contribute to drug use during imprisonment. Much of the extant literature examining the determinants of in-prison drug use, albeit generally scarce, has focused on individual (pre-prison) characteristics of male prisoners. The extent to which drug use is influenced by the prison environment remains largely unexplored – especially in women, who represent a particularly vulnerable population. The proposed mixed-methods study aims to redress these gaps and increase understanding of how drug use among women is shaped by the institutional context of prison. First, the relative importance of deprivation and importation factors in explaining drug use in female prisoners will be examined through multilevel quantitative analyses. Second, women’s perceptions of how the prison environment may impact upon their drug use, both positively and negatively, will be explored through qualitative in-depth interviews. Together, findings from this project have the potential to advance gender-sensitive theory and inform policy.