There are many factors resulting in a changing pattern of pneumonia. This varies from the impact of an aging population, patients surviving longer with underlying chronic disease, severe illness, and various causes of immunosuppression and the effect of new investigations, new antibiotics, and the recognition of new pathogens. Numerous studies have been performed over the last few years regarding the cause and outcome of community-acquired pneumonia (CAP). Marked variation in results has been seen related to the criteria used for defining and diagnosing pneumonia, the population studied, and the use of differing investigations and diagnostic criteria. This is particularly apparent when comparing the different incidence of pneumococcal infection as a cause of CAP in studies from different parts of the world. Extrapolation of the findings from the multicenter British Thoracic Society (BTS) study of pneumonia suggests that pneumococcal infection is more common than several studies suggest. Having said that, it is clear from examination of the many studies that CAP is a diverse disease and that different part of the world will have to develop individual management strategies based on a critical analysis of the best available study data appropriate to their local or national situation.