Chronic (non-communicable) diseases--principally cardiovascular diseases, cancer, chronic respiratory diseases, and diabetes--are leading causes of death and disability but are surprisingly neglected elements of the global-health agenda. They are underappreciated as development issues and underestimated as diseases with profound economic effects. Achievement of the global goal for prevention and control of chronic diseases would avert 36 million deaths by 2015 and would have major economic benefits. The main challenge for achievement of the global goal is to show that it can be reached in a cost-effective manner with existing interventions. This series of papers in The Lancet provides evidence that this goal is not only possible but also realistic with a small set of interventions directed towards whole populations and individuals who are at high risk. The total yearly cost of the interventions in 23 low-income and middle-income countries is about US$5.8 billion (as of 2005). In this final paper in the Series we call for a serious and sustained worldwide effort to prevent and control chronic diseases in the context of a general strengthening of health systems. Urgent action is needed by WHO, the World Bank, regional banks and development agencies, foundations, national governments, civil society, non-governmental organisations, the private sector including the pharmaceutical industry, and academics. We have established the Chronic Disease Action Group to encourage, support, and monitor action on the implementation of evidence-based efforts to promote global, regional, and national action to prevent and control chronic diseases.