Dementia of Alzheimer type (DAT), multiinfarct dementia (MID) and dementia occurring in the course of Parkinson's disease (PD +D) now make up one of the largest categories of chronic diseases in the elderly. In addition to the burden those illnesses impose on the affected individuals and their families they consume large socio-economic re- sources. In the light of all the above mentioned features, it seemed to us that a Symposium on behalf of the 125th Anniversary of Birth of Aloys Alzheimer was particularly well-suited to help to advance research on Alzheimer's disease and other dementias. This International Symposium combined with a Satellite Symposium about "Clinical Aspects of Alz- heimer Dementias" took place in June 1989 in Wiirzburg and has been organized by the Psychiatric Departments of the Universities of Wiirzburg and Munich (H. Beckmann, K. Maurer, P. Riederer, H. Hippius and H. Lauter) and the Department of Pathochemistry and General Neurochemistry of the University of Heidelberg (S. Hoyer). In the chapters which follow, thorough reviews of recognized authorities in the field of dementia are given in the four main fields of epidemiology, neuropathology, neurochemistry and clinics. This Symposium and the edition of this book would not have been possible without the generous support of E. Merck, Darmstadt. In particular we gratefully acknowledge the efforts undertaken by Mr. Hernandez-Meyer to organizing this symposium and to publish this book. Furthermore we are grateful to the secretarial help by Mrs. Moeslein, Miss Philipp and Miss Grabner.