During the last decade a multitude of studies concerning the dynamic changes in cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and intracranial pressure (ICP) in the acute phase after head injury have been published. These studies have been supplemented with studies of cerebral autoregulation, CO2 reactivity and barbiturate reactivity. Other investigations include studies of cerebrospinal fluid pH, bicarbonate, lactate and pyruvate. In this book experimental and clinical studies of the dynamic changes in CBF, CMRO2, CO2 reactivity and barbiturate reactivity are reviewed. The author's own clinical studies of the dynamic changes in CBF and cerebral metabolism are summarized and discussed, and the therapeutical implication as regards the use of artificial hyperventilation, sedation with barbiturate and mannitol treatment are discussed.