Background: NHS Regulations were amended in 2004, restricting access to secondary healthcare for refused asylum applicants. In recent years there have been substantial numbers of unsuccessful asylum applications from Zimbabwean nationals. HIV-positive Zimbabweans with insecure immigration status in the UK occupy a precarious medico-legal position, especially since HAART is not available to most in Zimbabwe. There has been little research on these policies or their effects on the lives of Zimbabwean HIV-positive women in the UK. Objectives: This thesis examines the development and implementation of UK policy relating to access to HIV-related services by Zimbabwean HIV-positive women with insecure immigration status, and explores how these policies influence women's healthcare. Methods: Three separate strategies were used for data collection. Policy analysis scrutinised 35 publicly available documents and additional material obtained through Freedom of Information (FOI) requests. Data for policy analysis were also collected through semistructured interviews with 24 HIV/immigration key informants. Further qualitative data were collected through semi-structured interviews with 13 Zimbabwean HIV-positive women with insecure immigration status. These different approaches allowed for data 'triangulation'. Results: Policy restricting access to healthcare for migrants is situated within three immigration control strategies of deterrence, internal control, and 'enforced discomfort'. Implementation of the policy has been limited by staff who interpret it to suit their own agendas. Access to HIV-care for Zimbabwean women seems to bear little relation to these policies, but their access to other health services and their wellbeing was influenced by a number of other socio-structural barriers associated with their immigration status. Conclusions: These results offer new evidence and theoretical models on the politics of immigration policy, the role of street-level bureaucrats as mediators of the gap between policy and practice, and on access to healthcare for migrants. There is a disjuncture between policy on entitlement and clinical practice, which may reflect a conflict between clinicians' duty of care and UK policy. Zimbabwean women's HIV- and migrant-status places them in a periphery, reducing the resources available to them that could mitigate some of the barriers they face.