National health systems need strengthening if they are to meet the growing challenge of chronic diseases in low-income and middle-income countries. By application of an accepted health-systems framework to the evidence, we report that the factors that limit countries' capacity to implement proven strategies for chronic diseases relate to the way in which health systems are designed and function. Substantial constraints are apparent across each of the six key health-systems components of health financing, governance, health workforce, health information, medical products and technologies, and health-service delivery. These constraints have become more evident as development partners have accelerated efforts to respond to HIV, tuberculosis, malaria, and vaccine-preventable diseases. A new global agenda for health-systems strengthening is arising from the urgent need to scale up and sustain these priority interventions. Most chronic diseases are neglected in this dialogue about health systems, despite the fact that non-communicable diseases (most of which are chronic) will account for 69% of all global deaths by 2030 with 80% of these deaths in low-income and middle-income countries. At the same time, advocates for action against chronic diseases are not paying enough attention to health systems as part of an effective response. Efforts to scale up interventions for management of common chronic diseases in these countries tend to focus on one disease and its causes, and are often fragmented and vertical. Evidence is emerging that chronic disease interventions could contribute to strengthening the capacity of health systems to deliver a comprehensive range of services-provided that such investments are planned to include these broad objectives. Because effective chronic disease programmes are highly dependent on well-functioning national health systems, chronic diseases should be a litmus test for health-systems strengthening. Copyright © 2010 Elsevier Ltd. All rights reserved.