Housing associations provide an example of the non-profit sector taking a major role in public service provision. This article tracks the implications for public accountability of their growth over the past 25 years to become the main providers of social housing. It uses the concept of institutional logics to highlight the conflicting accountability drivers they face and the organisational choices this is forcing them to make. Two competing logics are dominant in the current period: scale and efficiency and local accountability. Case studies map the impact of these competing logics on organisational change. The future development of the sector could involve displacement of one logic by the other, continued co-existence of the two logics or fragmentation of the field. A fourth possibility is that existing logics will be transformed by private sector market entry. mullins_2006.pdf