OBJECTIVE: To compare the cost-effectiveness of interventions to reduce pneumonia mortality through risk reduction, immunization and case management. METHODS: Country-specific pneumonia burden estimates and intervention costs from WHO were used to review estimates of pneumonia risk in children under 5 years of age and the efficacy of interventions (case management, pneumonia-related vaccines, improved nutrition and reduced indoor air pollution from household solid fuels). We calculated health benefits (disability-adjusted life years, DALYs, averted) and intervention costs over a period of 10 years for 40 countries, accounting for 90% of pneumonia child deaths. FINDINGS: Solid fuel use contributes 30% (90% confidence interval: 18-44) to the burden of childhood pneumonia. Efficacious community-based treatment, promotion of exclusive breastfeeding, zinc supplementation and Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae immunization through existing programmes showed cost-effectiveness ratios of 10-60 International dollars (I$) per DALY in low-income countries and less than I$ 120 per DALY in middle-income countries. Low-emission biomass stoves and cleaner fuels may be cost-effective in low-income regions. Facility-based treatment is potentially cost-effective, with ratios of I$ 60-120 per DALY. The cost-effectiveness of community case management depends on home visit cost. CONCLUSION: Vaccines against Hib and S. pneumoniae, efficacious case management, breastfeeding promotion and zinc supplementation are cost-effective in reducing pneumonia mortality. Environmental and nutritional interventions reduce pneumonia and provide other benefits. These strategies combined may reduce total child mortality by 17%.