Because its incidence increases with age and the current population ageing, community-acquired pneumonia will remain an important public health problem. The variability in the process of care is important. However, hospitalisation accounts for near 90% of the total annual cost. It is necessary to give to patients a rational process of care, supported by evidence of effectiveness, in order to guarantee the better quality of care and to control the costs. The chest radiograph is the cornerstone of the diagnosis of community-acquired pneumonia. The reason of this proposition is to avoid the overuse of antibiotherapy, in pathology such as lower-respiratory-tract infections. The use of the prognostic score index is recommended in emergency room to diminish the number of hospitalisations.