This article examines the bacteriology, clinical features, therapy for, and prevention of pneumonia in older patients. The discussion focuses on patients who develop pneumonia out of the hospital, including individuals with community-acquired pneumonia and health care-associated pneumonia. Health care-associated pneumonia incorporates patients who live in nursing homes when they develop pneumonia and in many instances requires management similar to nosocomial pneumonia. We have chosen not to discuss nosocomial pneumonia in older patients because it does not have distinctive features or a different management approach than when this illness arises in younger patients.