This report is the outcome of a one-year study commissioned by the Academy of Medical Sciences, the Medical Research Council and the Wellcome Trust to compare the economic benefits accruing to the UK from UK publicly and charitably funded medical research with the cost of that research. Understanding the nature, extent and processes involved in the return on investment in medical research has been largely neglected as an area of serious scientific study. Despite a growing international interest in this area there has been relatively little formal analysis of the returns to medical research, particularly in Europe. The study reported here represents an initial step towards rectifying that situation. The limitations of available data, the questions around methodology, and the issues raised by the authors' analysis lead them to identify some key elements for the future research agenda in this area, most prominently: --research funders need to develop and use a standardised (and mapped) way of classifying research funding; --further research needs to be undertaken to understand the time lag between research expenditure and health gain;-- the 'spillover' effects of public and charitable research expenditure on the national economy need further, UK-focused, empirical investigation; --a deeper understanding of the international flows of knowledge and influence would be valuable; --the importance of local research in terms of absorptive capacity: further research to test this would be very valuable, particularly to the health care system and the National Institute for Health Research; --researchers need to understand additionally, what are the global health benefits from UK medical research.