This paper defines quality of health care. We suggest that there are two principal dimensions of quality of care for individual patients; access and effectiveness. In essence, do users get the care they need, and is the care effective when they get it? Within effectiveness, we define two key components--effectiveness of clinical care and effectiveness of inter-personal care. These elements are discussed in terms of the structure of the health care system, processes of care, and outcomes resulting from care. The framework relates quality of care to individual patients and we suggest that quality of care is a concept that is at its most meaningful when applied to the individual user of health care. However, care for individuals must placed in the context of providing health care for populations which introduces additional notions of equity and efficiency. We show how this framework can be of practical value by applying the concepts to a set of quality indicators contained within the UK National Performance Assessment Framework and to a set of widely used indicators in the US (HEDIS). In so doing we emphasise the differences between US and UK measures of quality. Using a conceptual framework to describe the totality of quality of care shows which aspects of care any set of quality indicators actually includes and measures and, and which are not included.