&NA;The main purposes of this study were to evaluate pressure‐volume relations and cerebrospinal fluid (CSF) dynamics in patients with head injury and to evaluate the pressure‐volume index (PVI) in that context. Sixteen head‐injured patients underwent (a) continuous intracranial (intraventricular) pressure (ICP) monitoring, (b) studies of the PVI and the width of the pulse amplitude, and (c) studies of CSF dynamics determined by the PVI technique or controlled withdrawal and expressed as resistance to the outflow of CSF (Rout). In this study, the PVI technique proved safe and relatively simple. The PVI based on bolus injections was significantly greater than the PVI based on CSF withdrawal. The PVI varied independently of clinical course, outcome, and ICP. The ICP pulse amplitude increased linearly with the ICP. It was not possible to establish any clinically useful correlation between pulsatile ICP changes and intracranial compliance (PVI). There was a linear correlation between ICP and Rout. (Neurosurgery18:17‐24, 1986)