Free radicals appear to play a mojor role in many neurological (and non- neurological) dieseases. Both acute and degenerative disorders are thought to involve free radicals reactions in tissue injury (for a list see this book page 18). This issue is very important for basic science and for therapeuthic approach as well. In order to review and discuss the place of free radicals in psychiatry and neurology, a joint meeting was initiated by the World Health Organization and the Fondation Ipsen in Paris on June 17-18, 1991. This book contains the papers presented during this meeting. Although the papers included in this volume have been produced in the framework of WHO/Fondation Ipsen review of knowledge about free radicals and brain disorders, they express the views of the individual authors rather than a consensus of the participants at the meeting. They do not necessarily represent the decision or stated policy of the World Health Organiszation or the Fondation Ipsen. The editors wish to express their appreciation to Mrs Mervaillie for the organization of the meeting and Mrs M.-L. Gage for her editorial assis- tance. L. Packer, L. Prilipko, Y Christen Contents Free Radical Scavengers and Antioxidants in Prophylaxy and Treatment of Brain Diseases L. Packer ……………………………………. 1 Reactive Oxygen Species and the Central Nervous System B. Halliwell …. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 . . . . . . . . .