The pursuit of equity of access to health care is a central objective of many health care systems. This paper first sets out a general theoretical framework within which equity of access can be examined. It then applies the framework by examining the extent to which research evidence has been able to detect systematic inequities of access in UK, where equity of access has been a central focus in the National Health Service since its inception in 1948. Inequity between socio-economic groups is used as an illustrative example, and the extent of inequity of access experienced is explored in each of five service areas: general practitioner consultations; acute hospital care; mental health services; preventative medicine and health promotion; and long-term health care. The paper concludes that there appear to be important inequities in access to some types of health care in the UK, but that the evidence is often methodologically inadequate, making it difficult to draw firm conclusions. In particular, it is difficult to establish the causes of inequities which in turn limits the scope for recommending appropriate policy to reduce inequities of access. The theoretical framework and the lessons learned from the UK are of direct relevance to researchers from other countries seeking to examine equity of access in a wide variety of institutional settings.