The onset of an epileptic seizure has become a matter of prime interest in the last two decades. For successful therapy it is of the greatest importance to understand how the different inhibitory mechanisms involved in the normally functioning brain are carried out, and how the devastating avalanche of the seizure activity may overrun wide areas of grey matter. This problem of how an attack may arise has been dealt with in several monographs, but from different points of view: on the one hand chiefly from the viewpoint of the clinical EEG (GAsTAuT et al. 1969), on the other hand from the viewpoint of experimental epilepsy, starting with the activities observed at the level of the nerve cell (JASPER et al. 1969). This volume has quite a different perspective. It contains the papers and discussions presented at a Symposium organized by the Austrian Academy of Sciences, the aim of which was to arrive at a better understanding of some of the electrical phenomena accompanying the epileptic seizure.