Complications are the major causes of illness and death after burning and most of them stem from the burn wound. Their origin and importance are reviewed with emphasis on problems and growing points in knowledge. Fluid leakage from the circulation into the burn is the cause of hypovolemic shock, but the underlying permeability changes in the burn are only partly understood. Other nonbacterial complications include acute cardiac failure, acute anemia, hemolytic jaundice, renal failure, encephalopathy, complex hypermetabolic effects including pseudodiabetes, gastric and duodenal ulceration, deep vein thrombosis and pulmonary embolism, pulmonary and glomerular microthrombosis, hepatic jaundice, and arterial thrombosis. Involvement of the airway in conflagrations carries special hazards like glottic edema and inhalation of irritant fumes. Nowadays, bacterial causes are dominant and these remain the main challenge. Bacterial infection and invasion of the burn are usually responsible for septicemia, bronchopneumonia, and pyelonephritis although other sources also contribute. Indirect manifestations of septicemia include paralytic ileus, acute gastric dilatation, toxic myocarditis, and some cases of renal failure. Therapeutic complications like agranulocytosis, thrombocytopenia, and colitis occur at times. High concentrations of oxygen given therapeutically can produce fatal aseptic hypoxic pneumonitis. © 1979 by The Williams & Wilkins Co.