Pre-eclampsia and eclampsia represent a syndrome with progressive pregnancy-induced hypertension. They are associated with considerable morbidity and mortality. The pre-eclampsia/eclampsia syndrome has been hypothesized to reflect a subtype of hypertensive encephalopathy. Additionally, an endothelial dysfunction with impaired cerebral autoregulation has been proposed. Neurological symptoms in hypertensive encephalopathy have been attributed to marked vasospasm or forced vasodilatation. This study was undertaken to evaluate the changes in cerebral hemodynamics due to this syndrome. Twelve patients with pre-eclampsia/eclampsia syndrome, five of them with a concomitant syndrome involving hemolysis, elevated liver enzymes and low platelets (HELLP syndrome), were investigated. Mean blood flow velocities of the middle, anterior and posterior cerebral arteries were assessed bilaterally by means of a 2-MHz, pulsed Doppler ultrasound device. After the initial diagnosis, follow-up examinations were performed twice a week until delivery, and then weekly over a 4-week period postpartum. Intracranial arterial blood flow velocities were elevated in ten out of 12 patients. Values of up to twice the normal flow velocities were observed in individual cases. Flow velocities correlated with the systemic arterial blood pressure (r = 0.75, p = 0.008). Eight patients showed pathologically increased flow velocities despite a mean arterial blood pressure below 150 mmHg. Our preliminary findings suggest that a forced vasodilatation, probably due to passive overdistension of cerebral arterioles and vasogenic edema rather than vasospasm, is responsible for the observed high cerebral flow velocities. We hypothesize that endothelial dysfunction plays a crucial role in the altered cerebral hemodynamics in the pre-eclampsia/eclampsia syndrome.