Global mortality in children younger than 5 years has fallen substantially in the past two decades from more than 12 million in 1990, to 6•9 million in 2011, but progress is inconsistent between countries. Pneumonia and diarrhoea are the two leading causes of death in this age group and have overlapping risk factors. Several interventions can eff ectively address these problems, but are not available to those in need. We systematically reviewed evidence showing the eff ectiveness of various potential preventive and therapeutic interventions against childhood diarrhoea and pneumonia, and relevant delivery strategies. We used the Lives Saved Tool model to assess the eff ect on mortality when these interventions are applied. We estimate that if implemented at present annual rates of increase in each of the 75 Countdown countries, these interventions and packages of care could save 54% of diarrhoea and 51% of pneumonia deaths by 2025 at a cost of US$3•8 billion. However, if coverage of these key evidence-based interventions were scaled up to at least 80%, and that for immunisations to at least 90%, 95% of diarrhoea and 67% of pneumonia deaths in children younger than 5 years could be eliminated by 2025 at a cost of $6•715 billion. New delivery platforms could promote equitable access and community platforms are important catalysts in this respect. Furthermore, several of these interventions could reduce morbidity and overall burden of disease, with possible benefi ts for developmental outcomes.