Severe community-acquired pneumonia (CAP) is still a serious disease with a high mortality rate, especially in developing countries. Children under 5 years are more prone to severe CAP. In this article, the authors review the definition and clinical criteria used in the initial evaluation and decision to hospitalize patients. The diagnosis approach requires only a limited number of laboratory tests before initiating the supportive measures and wide spectrum antimicrobial therapy. If the patient fails to respond favorably 48-72 hours after initiating therapy, more invasive investigations are indicated. After resolution, an immunological evaluation is warranted.