Community-acquired pneumonia is an important public health concern and a recent focus of clinical practice guidelines. What has become clear from this renewed focus of attention is that a subgroup of patients with community-acquired pneumonia have severe disease with a differing spectrum of pathogens and prognosis. This article reviews the definition, bacteriology, diagnostic approach, and treatment of patients categorized as having severe community-acquired pneumonia. Although some of what is discussed is controversial and the literature in this area continues to expand, we focus on an evidence-based approach to this clinical problem.