Cerebrospinal fluid (CSF) pressure was recorded in 149 patients and arterial blood pressure (BP) in 11 patients while moving between lateral and sitting positions. Rapid tilting initiated waves in BP and CSF filling pressure. The postural CSF pressure wave manifested itself either as a transient or as a stationary wave similar to a plateau wave. When patients sat up, transient waves had amplitudes up to 550 and stationary waves up to 1000 mm H2O. When they lay down, transient waves had amplitudes up to 800 mm H2O. Stationary waves were found only among patients with elevated intracranial pressure and a diseased brain. The waves were mainly caused by changes in cerebral blood volume probably reflecting the postural BP wave and brain autoregulation. Most patients with stationary and large transient waves also manifested clinical symptoms. These symptoms were aggravated when a craniospinal block developed in the sitting position, and were reduced or avoided when the tilting was performed slowly over 2 to 3 minutes.