The private health care market in the United Kingdom is a multi-billion pound industry whose dynamics remain largely unexamined. This is so even though the boundaries between the public and private sectors are becoming increasingly blurred, particularly in England. Given the growing importance of this sector, the policy community needs to know more about the nature of private health care in the UK, how well the private market operates and how successful have been the various attempts within it to improve value for money and health care quality, given that private health care has traditionally been seen by many citizens as unaffordable. In particular this thesis traces recent efforts by the British United Provident Association (Bupa) to reshape the UK private healthcare market. The account provided draws on the author's experience as a senior Bupa manager involved in planning and implementing such changes. The thesis describes a series of Bupa initiatives designed to change provider behaviour in pursuit of improved quality and value-for-money, and the difficulties and obstacles encountered. The latter often centred on tensions or confrontation between the insurer and professional providers that are discussed in relation to the wider literature on the social and economic organisation of health care markets. An attempt has been made to draw some general conclusions via an empirical study of the role and limitations of market-based changes within the UK private sector. The broad conclusion is that the private market in the UK exemplifies those features of health care seen throughout the developed world that create imperfect market conditions. As such the market is highly resistant to insurer initiatives that would reverse the longstanding trend for premiums to rise above the rate of inflation. It is considered unlikely given the current market structure that any insurer, including Bupa, can escape these constraints in the short term. However, Bupa has implemented some successful initiatives that suggest that longer-term incremental change is possible.