The case of a 56 year old female suffering from a carcinomatous meningitis with recurrent attacks of unconciousness is presented. The ischemic nature of the attacks was substantiated through a simultaneous recording of ICP, systemic arterial blood pressure, and EEG. Every syncope was clearly accompanied by 1) a typical ICP plateau-wave, 2) a systemic blood pressure wave of lower amplitude, 3) a considerable correlative diminution of the cerebral perfusion pressure and 4) a slowing down of the EEG. These phenomenons could be provoked by intraventricular injections of a few milliliters of artificial CSF, whereas a ventriculo-peritoneal shunting made them disappeared. The role played by the disturbances of the CSF flow in the production of the plateau waves is discussed.