In 58 female patients with the primary empty sella (PES) syndrome, a study of the CSF dynamics was done by evaluating both the absorptive reserve by a lumbar infusion test at constant rate, and/or the ICP increase occurring during REM phase of nocturnal physiological sleep. In 33, prolactin (PRL) dynamics were also investigated evaluating both the response to sequential stimulating test with thyrotropin-releasing hormone (TRH) and metoclopramide (MCP) and/or the circadian variation of PRL levels. Impairment of CSF dynamics was found in the 84% who had a hormonal pattern characterized by an increase of the PRL response to TRH and MCP and a decrease of the PRL circadian variation. Twenty-one patients with impaired CSF dynamics underwent CSF shunting procedures with disappearance of the signs of intracranial hypertension. They also had restoration of normal PRL dynamics but the endocrine alterations improved only moderately. Altered CSF dynamics play a role in the pathogenesis of the PES syndrome. A correlation between elevated ICP and the hypothalamo-hypophyseal control of PRL secretion may exist.