BACKGROUND: In July, 2003, the Bellagio Study Group on Child Survival estimated that the lives of 6 million children could be saved each year if 23 proven interventions were universally available in the 42 countries responsible for 90% of child deaths in 2000. Here we assess the cost of delivering these interventions, and discuss whether the achievement of the Millennium Development Goal (MDG) for child survival falls within the financial capacities of donors and developing countries. METHODS: All child survival interventions shown to reduce mortality from the major causes of death in children younger than 5 years were incorporated into a delivery timetable comprised of 18 contacts between a child or mother and a health-care provider in the period from before birth until the child reaches 5 years. The running costs of delivering the interventions at universal coverage levels were calculated as the sum of unit costs for drugs and materials, delivery costs, and programme management and support costs, including supervision. We estimated the cost of providing interventions at coverage levels reported for 2000 and the additional costs of providing services at universal coverage levels. FINDINGS: USD 5.1 billion in new resources is needed annually to save 6 million child lives in the 42 countries responsible for 90% of child deaths in 2000. This cost represents 1.23 dollars per head in these countries, or an average cost per child life saved of 887 dollars. Sensitivity analyses for salary levels for community delivery agents, drug costs, and coverage rates for 2000 were used to develop uncertainty estimates around the USD 5.1 billion annual price tag that range from about 3.1 billion dollars to 8.0 billion dollars. INTERPRETATION: Achieving the MDG for child survival is affordable for donors and developing countries. Scaling up health delivery is the challenge, and, along with the lack of funds, will be the limiting factor in reducing child mortality by two-thirds by 2015.