Severe acute respiratory syndrome (SARS) has been described as the first major emerging infectious disease of the twenty-first century. Having initially emerged, almost unnoticed, in southern China, it rapidly spread across the globe. It severely tested national public health and health systems. However, it also resulted in rapid, intensive international collaboration, led by the World Health Organization, to elucidate its characteristics and cause and to contain its spread. The UK mounted a vigorous public health response. Some particular issues concerned: the practicalities of implementing exit screening had this been required; the likely efficacy of this and other control measures; the legal base for public health action; and the surge capacity in all systems should the disease have taken hold in the UK. We have used this experience of 2003 to inform our preparation of a framework for an integrated, escalating response to a future re-emergence of SARS according to the levels of disease activity worldwide. Recent cases confirm that SARS has not "gone away". We cannot be complacent about our contingency planning.