Pneumonia is one of the leading causes of mortality and hospitalization among US adults. The decision to admit patients from the emergency department is a major one because of its impact on patients and the hospital. The diagnosis of pneumonia is often clinical and based on symptoms and signs combined with radiographic findings. There are multiple severity assessments available that can guide treatment, prognosis, and disposition. Viruses are an important cause of pneumonia and require early recognition and treatment. The recommended treatment for community-acquired pneumonia includes a beta lactam plus a macrolide or a respiratory fluoroquinolone.