ABSTRACT.Modern noninvasive imaging techniques and especially the CAT scan enable us to demonstrate and localize with high accuracy intracranial morphological changes. Ultrasonic investigations (Doppler sonography) permit the assessment of the function of extracranial and even intracranial portions of the major arteries of the brain. The regional cerebral blood flow can be measured with noninvasive methods (Xenon clearance).With this information at hand, we have also achieved a better understanding of the EEG and its contribution to the evaluation of patients with cerebrovascular disorders.