Childhood acute community-acquired pneumonia is one of the leading causes of morbidity and mortality in developing countries. In children who have not received prior antibiotic therapy, the main bacterial causes of clinical pneumonia in developing countries are Streptococcus pneumoniae and Haemophilus influenzae type b (Hib), and the main viral cause is respiratory syncytial virus (RSV), but estimates of their relative importance vary in different settings. The only vaccines for the prevention of bacterial pneumonia (excluding vaccines for pertussis and measles) are Hib and pneumococcal conjugate vaccines (PCV). In children with human immunodeficiency virus (HIV) infection, bacterial infection remains a major cause of pneumonia mortality; however, Pneumocystis jirovecii and Mycobacterium tuberculosis are important causes of pneumonia in them. Studies of bacterial aetiology of acute pneumonia in severely malnourished children have implicated Klebsiella pneumoniae, Staphylococcus aureus, S. pneumoniae, Escherichia coli, and H. influenzae, with very few data on the role of respiratory viruses and tuberculosis. Studies of neonatal sepsis suggest that Gram-negative enteric organisms, particularly Klebsiella spp., and Gram-positive organisms, mainly pneumococcus, group b Streptococcus and S. aureus are causes of neonatal pneumonia. Many of the developing countries that ranked high in pneumonia mortality are preparing to introduce new pneumonia vaccines with support from Global Alliance for Vaccine and Immunization (GAVI Alliance), plan for the expansion of community-based case management and have ambitious plans for strengthening health systems. Assurance that these plans are implemented will require funding and continued public attention to pneumonia, which will help contribute to a substantial decline in childhood pneumonia deaths.