The Symposium on Brain Edema has been organized by the Osterreichische Arbeitsgemeinschaft fur Neuropathologie and by the Problem Commission for Neuropathology of the World Federa­ tion of Neurology. We would like to express our thanks to Dr. L. van Bogaert, president of the W.F.N., for his great interest in the design of this conference and for his energetic support. One of the aims ofthe Problem Commission for Neuropathology has been to contribute to the advances in various problems which are becoming ripe for elucidation by experts in different fields. The idea of the Symposium on Brain Edema has as its background a compelling necessity to elucidate this subject which is clinically so important and neuropathologic ally so poorly understood. It was hoped that this could be achieved by a multidisciplinary approach involving a variety of aspects to be discussed and correlated. Brain edema, being an abnormal cerebral condition, belongs basically to the sphere of neuropathology, but to be successful in our endeavors we had to apply neuropathology in its most modern and widest terms. By this we understand that such neuropathology includes the study of all abnormal phenomena in the nervous tissue related to the structural alterations, and by "structural" we mean not only tissual or cellular ones but also changes on ultrastructural and molecular levels. Thus we needed close and integrated coopera­ tion of experts in fields such as neurohistology, histochemistry, electron microscopy, neurochemistry, and neurophysiology.