Respiratory problems occur commonly in association with severe head injury. Seven easily measured parameters for the diagnosis of respiratory insufficiency are outlined. Certain central and peripheral causes of insufficient ventilation are analyzed, including head trauma and drug overdose as central sources and aspiration, pulmonary edema, disseminated intravascular coagulopathy, fat embolism, chest trauma and iatrogenic complications as peripheral causes. Establishment of the diagnosis and management of the problems within each category are discussed.