Epidural intracranial pressure (ICP) was monitored chronically for up to 6 weeks in conscious, unrestrained rabbits. Hydrocephalus was induced by injecting viscous silicone oil into the cisterna magna. Following injection, ICP remained significantly elevated for only 2 days. Thereafter, the baseline ICP of hydrocephalic rabbits returned to control values. During the hydrocephalic period, however, ICP exhibited instability and transient elevations. ICP characteristics of this model of experimental hydrocephalus resemble those of chronically hydrocephalic humans.