This book represents the fourth ina series of international conferences related to Alzheimer's (AD) and Parkinson's (PO) diseases. The first one took place in EHat, Israel in 1985; the second in Kyoto, Japan, in 1989; and the third in Chicago, IL, USA in 1993. This book incorporates the proceedings of the Fourth International Conference on Pro- gress in Alzheimer's and Parkinson's Diseases, held in EHat, Israel, on May 18-23, 1997. This Conference was the 41st in the series of annual OHOLO Conferences sponsored by the Israel Institute for Biological Research (IIBR). It was also conducted under the aus- pices of the Alzheimer's Association Ronald and Nancy Reagan Research Institute, USA. The Conference was attended by 550 participants from 28 countries, representing a broad spectrum of research interests; and included a well-balanced representation from aca- demia, clinical institutions and pharmaceutical industry. The four-and-one-half day meeting served as an excellent medium for surveying the current preclinical and clinical develop- ments in AD, PO, and other related disorders. The scientific program was divided into 24 oral sessions and daily poster sessions. The conference culminated in a round table discus- sion. There were 122 talks and 161 posters. This book incorporates a combination of both.