OBJECTIVE One of the key goals of the current reforms in the English National Health Service (NHS) under the Health and Social Care Act, 2012, is to increase the accountability of those responsible for commissioning care for patients (clinical commissioning groups (CCGs)), while at the same time allowing them a greater autonomy. This study was set out to explore CCG's developing accountability relationships. DESIGN We carried out detailed case studies in eight CCGs, using interviews, observation and documentary analysis to explore their multiple accountabilities. SETTING/PARTICIPANTS We interviewed 91 people, including general practitioners, managers and governing body members in developing CCGs, and undertook 439 h of observation in a wide variety of meetings. RESULTS CCGs are subject to a managerial, sanction-backed accountability to NHS England (the highest tier in the new organisational hierarchy), alongside a number of other external accountabilities to the public and to some of the other new organisations created by the reforms. In addition, unlike their predecessor commissioning organisations, they are subject to complex internal accountabilities to their members. CONCLUSIONS The accountability regime to which CCGs are subject to is considerably more complex than that which applied their predecessor organisations. It remains to be seen whether the twin aspirations of increased autonomy and increased accountability can be realised in practice. However, this early study raises some important issues and concerns, including the risk that the different bodies to whom CCGs are accountable will have differing (or conflicting) agendas, and the lack of clarity over the operation of sanction regimes.