Acute respiratory infections kill 4 million children every year in developing countries, and most of these deaths are caused by pneumonia. This huge loss of life goes virtually unnoticed, despite the fact that we have two very effective ways of preventing many of the deaths from pneumonia: Haemophilus influenzae type b vaccine, and standardised antibiotic treatment regimens. Although H. influenzae type b vaccine has virtually eliminated diseases caused by this organism in children in developed countries, failure to appreciate the importance of this organism and the high cost of the vaccine has meant that it has not been used in developing countries; urgent steps need to be taken to ensure that children in developing countries receive H. influenzae vaccine. Streptococcus pneumoniae is a major cause of fatal pneumonia in developing countries. Controlled trials are needed to define the role of unconjugated 23-valent S. pneumoniae vaccine, and the new conjugate vaccine must be made available to children in developing countries soon after it is licensed. The World Health Organization has developed simple and effective guidelines for the treatment of pneumonia which have been incorporated into its Integrated Management of Childhood Illness strategy, and this programme should be strongly supported. In developed countries, acute respiratory infections are the leading cause of morbidity. The cost of these infections is enormous, because of lost earnings and the cost of treatment. There is an urgent need for systematic evaluation of existing knowledge about acute respiratory infections in developed countries, so that this knowledge can be applied to prevention and treatment. Approximately 75% of antibiotics are prescribed for acute respiratory infections, and many of these prescriptions are unnecessary. Unnecessary use of antibiotics is very expensive, and it has contributed to the rapid increase in resistance which has already made some bacteria resistant to all antibiotics. Rational guidelines for antibiotic prescribing need to be developed, and steps taken to see that they are followed. There should be greatly increased use of the existing influenza and pneumococcal vaccines in high risk groups in developed countries. New vaccines against pertussis, S. pneumoniae, non-serotypable H. influenzae, and respiratory syncytial virus have been developed and need to be carefully evaluated. Acute respiratory infections are responsible for 8.2% of the world's total burden of disability and premature death, but they receive only 0.15% of the research and development budget for health. More resources should be allocated to research on acute respiratory infections. Drug therapy has little effect on the course of viral upper respiratory tract infections. Worldwide, US$8 billion is wasted every year on drugs used to treat the symptoms of acute respiratory infections.