Intracranial pressure monitoring with an intra-ventricular catheter, an external transducer and a continuous chart recorder was undertaken in 15 patients with acute brain damage and in six patients suspected of suffering from long-standing raised intracranial pressure. In the acute cases, monitoring was useful in the diagnosis of raised intracranial pressure and in the assessing of the efficacy of its treatment. In the chronic cases, the clinical suspicion of raised pressure was confirmed or refuted without doubt. Complications were minimal, and the method was judged to be of considerable value in selected cases.