Bacterial infection is a common and serious problem in burn victims who survive the shock phase of thermal injury. Our experimental work, plus the clinical studies of others, suggests that the gut can serve as a reservoir for systemic infections caused by bacteria that cross (translocate) the gastrointestinal (GI) epithelium. Bacterial translocation from the GI tract does not normally occur in the healthy animal owing to (1) the presence of an indigenous GI microflora preventing bacterial overgrowth, (2) an intact intestinal epithelial barrier, and (3) normal host immune defenses. However, a thermal injury, as well as other stressors, can result in the disruption or impairment of any of these protective mechanisms, potentially leading to lethal systemic infections with bacteria colonizing the gut.