There is increasing pressure on researchers and research funding bodies to demonstrate the value of research. Simple approaches, consistent with the biomedical paradigm, based on relating the cost of research to its supposed impact are being investigated and adopted in laboratory and clinical research. While this may be appropriate in such research areas, it should not be applied to health services research which aims to alter the ways policy-makers and managers think about health, disease and health care or, as John Maynard Keynes put it, 'the gradual encroachment of ideas'. By considering six fundamental assumptions about health care that have been successfully challenged and overturned over the past few decades, the profound and sustained impact of health services research can be demonstrated. The application of economic models of 'payback' would fail to recognize such contributions which, in turn, could threaten future funding of health services research.