Selective decontamination of the digestive tract (SDD) evolved into evidence-based medicine as a tool to prevent infections in critically ill patients. It significantly reduces mortality, pneumonia, bloodstream infections and the onset of resistance if the full four-component regimen is used. The use of only oral decontamination may reduce the incidence of pneumonia, but it has no significant impact on mortality. Moreover, the full SDD protocol significantly reduces the fecal carriage of multiresistant aerobic Gram-negative bacteria, whereas oral decontamination only is associated with increased carriage of multiresistant aerobic Gram-negative bacilli.