Hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), and health care–associated pneumonia (HCAP) cause 25% of all infections in the intensive care unit and are the basis for 50% of all antimicrobials prescribed in the hospital. These are primarily bacterial infections and are associated with high morbidity and mortality rates. However, pneumonias occurring before the fifth day of hospitalization are generally caused by organisms that are more susceptible to antimicrobials and have a better prognosis than those occurring on or after the fifth hospital day. The diagnostic and therapeutic approaches to HAP, VAP, and HCAP are similar.