In this chapter, we focus on the major reforms intended to ensure the sustainability of health care in Denmark between 2000 and 2020 and the evidence for the effectiveness of these reforms. We take a broad definition of sustainability and include reforms that aimed to improve the productivity of the health care sector both in terms of increasing activity for the same set of inputs and in terms of improving the quality of care. A characterisation of the Danish health care system as having gone through evolution rather than revolution (Pedersen, Christiansen, & Bech, 2005) is, with one exception, still true today, and reforms have been relatively few. As we demonstrate there is a relative lack of formal evaluations of these reforms. In the first decade of the period, the majority of new policy measures aimed to increase the quantity of care provided by the health care sector. With the introduction of diagnosis-related groups (DRGs) to measure hospital activity, a wave of reforms created a stronger link between activity and hospital reimbursement, and introduced additional incentives for increasing activity, alongside requirements for increased technical efficiency. A centralisation reform in 2007 reduced the number of administrative units and saw the beginning of a development that would also lead to fewer hospital units. Procurements of medicines were professionalised, and a national council was established to consider the use of expensive hospital medicine. In the second-half of the period, policy makers began questioning whether increased activity was always for the better, and slowly began experimenting with initiatives that would shift the focus to the quality and appropriateness of care. As in many other countries, this move occurred in the light of a realisation of a shift in the demographic structure of the country and the change this was expected to create for the future demand for health care. Although some empirical evidence exists, it is striking that few of the changes to the health care sector has been subject to formal academic evaluation – especially when considering the availability of high quality nationwide micro data. We point to a number of important lessons that could be drawn from the Danish experiences. However, the greatest potential for research into the sustainability of health care in the Danish setting is probably still to be realised by taking advantage of the possibilities of linking micro data on individuals’ health care utilisation, schooling outcomes and labour supply, with the possibility of following individuals across decades. For example, Danish micro data make it possible to follow newborns in 1990 until they reach adulthood and simultaneously follow their parents from adulthood until they reach 60 years of age where the prevalence of chronic diseases begins to show.