Pneumonia is a lung infection. Most patients get better with antibiotics, but some develop serious complications or die. Factors that increase the chance of dying of pneumonia include older age, living in a nursing home, having other illnesses (especially cancer), and having certain abnormal physical examination or test results. Experts agree that patients at high risk for pneumonia complications should be hospitalized and patients at low risk should get treatment at home. Guidelines are recommendations for managing medical conditions that are based on studies that identify the types of care that work best. For pneumonia, 1 guideline identifies the types of patients who require hospitalization and those who can safely get treatment at home. Other guidelines recommend tests and treatments for patients with pneumonia. Unfortunately, many patients with pneumonia do not get treatment that agrees with guidelines. Hospitals are trying to identify strategies to improve pneumonia care.