This thesis explores the prison-to-community transition experience after short-term incarceration, from the perspective of men with co-occurring mental illness and substance use disorder in Queensland, Australia. A specific focus was to examine the impact of systems and structures on the individual experience of transition. Prior research has established that people with co-occurring mental illness and substance use are overrepresented in the Australian prisoner population. It is also known that transition from prison to community for the general custodial population is a time of vulnerability, with increased risk of substance use, homelessness, unemployment, reincarceration and post-release death. All of these risks are compounded for prisoners with co-occurring disorders who are also at risk of a range of poor criminal justice outcomes and losing contact with mental health services after release.Review of the literature indicates a tendency for research to focus on recidivism as an outcome and emphasise either individual risk behaviour or social and structural factors influencing prison-to-community transition. Interventions during transition for the current population have traditionally been based on the criminalisation hypothesis, with a focus on increased provision of mental health services in prison and an emphasis on continuity of care in the community. There is a growing recognition in the international literature that the issues are much broader than mental illness; however, there is a lack of clarity as to how to respond to the complex needs of this population. Research exploring the perspective of men with cooccurring severe mental illness and substance use disorder during their prison-to-community transition experience has rarely been undertaken.The conceptual framework developed for this study shifts the emphasis away from recidivism towards recovery and wellbeing through a lens of individual action, but only in the context of the potential for systems and structures to impact on the ability of individuals to exercise agency. A qualitative method was used comprising repeat in-depth interviews with 18 men: within 1 month prior to leaving prison, within 2 weeks post-release and at 3 months postrelease. Three themes characterised the transition experience of participants: "hoping against hope"; "adrift in freedom"; and "the slippery slope". Participants reported leaving the predictable and routine life in prison where they hoped for a better life after release, to an uncertain, unstable and isolated environment in the community, eventually sliding into drug use, chaos and despair. The risk environment framework (Rhodes, 2009) and structuration theory (Giddens, 1984) were employed to understand how participants were caught in a complex dynamic between their individual risk behaviour and broader structural risk iii environments. This thesis proposes that a web of interrelated factors contributed to participants in the study as "ambivalent agents" who were suspended between the two worlds of priso...