A new model of the cerebrospinal fluid (CSF) circulation is proposed, implying that the main absorption of CSF occurs through the brain capillaries. This model is based on recent observations of CSF dynamics using radionuclide cisternography and cardiac gated magnetic resonance imaging. Magnetic resonance imaging of communicating hydrocephalus has demonstrated a highly significant decrease of CSF flow through the foramen magnum, which is explained by decreased expansion of the intracranial arteries. This invariable finding in combination with the new view of the CSF-circulation makes a hemodynamic pathogenesis of hydrocephalus very probable. Communicating hydrocephalus may be caused by any process that restricts the arterial pulsations and is therefore termed restricted arterial pulsation hydrocephalus. In obstructive hydrocephalus, the ventricular dilatation leads to a compression of the cortical veins and consequently is termed venous congestion hydrocephalus. Based on these considerations, a new concept of pharmacological treatment of hydrocephalus is proposed by using a selective venous constrictor.