Community-acquired pneumonia remains a common and serious illness, which affects children of all age groups. The spectrum of causative organisms is wide and it differs according to the age of the patients. With the advent of new and improved diagnostic techniques our understanding of the aetiology of the disease has been improved considerably. Viruses have been shown to cause up to 90% of pneumonias, especially in the first year of life, with the respiratory syncytial virus to be the most important pathogen and this percentage decreases to approximately 50% by school age. Viral pneumonias frequently are complicated by bacterial infections and mixed infections are identified in 30% of the cases. The precise role of viruses and bacteria in these cases, remains to be clarified.