Partnership working has become a central feature of British social welfare policy since 1997. Although this development is applicable to all areas of public welfare, nowhere is it more evident than in the planning and provision of care that overlaps health and social services. The literature survey described in the present paper focused on research examining the impact of partnership working in these areas to assess the evidence concerning its effects and to investigate how partnership ‘success’ is conceptualised. The literature conceptualised the success of partnerships in two main ways: (1) process issues, such as how well the partners work together in addressing joint aims and the long-term sustainability of the partnership; and (2) outcome issues, including changes in service delivery, and subsequent effects on the health or well-being of service users. The authors found that research into partnerships has centred heavily on process issues, while much less emphasis has been given to outcome success. If social welfare policy is to be more concerned with improving service delivery and user outcomes than with the internal mechanics of administrative structures and decision-making, this is a knowledge gap that urgently needs to be filled.