There has been a shift in the theoretical debates around the ways in which organisations deliver the state's objectives of providing health and social care services for its citizens, focusing on issues of welfare governance and the encouragement of partnership working between organisations. This article develops these theories by focusing on developments in primary health and social care policy in the UK, which have undergone a radical change recently. Responsibility for commissioning health care services now falls to primary care groups and trusts (PCG/Ts), run by general practitioners, other primary care practitioners, managers and lay members, and there is some pressure on primary care groups and primary care trusts to engage in partnership working with social services, for example, to cut hospital waiting lists or provide intermediate care services. One policy option is for these organisations to form Care Trusts, integrating the commissioning of health and social care for older people and ending the historical organisational divisions between health and social care in the UK. This paper examines evidence from the first stage of a 3-year longitudinal quantitative and qualitative study of the development of partnership working between PCG/Ts and social services departments in England. It examines whether the evidence suggests that the integration of health and social care is feasible or desirable in older people's services.