There is increasing evidence that links together various common neurodegenerative diseases, such as Parkinsons and Alzheimers diseases. Finding common themes in the pathophysiology of such disorders is increasingly important. This text addresses such a common themethe proteasome. Since the discovery of the proteasome some 20 years ago, significant strides have been made in our understanding of proteasome biology and our understanding of the role the proteasome plays in a wide variety of biochemical events. Taken together, these studies have confirmed an important role for the proteasome in the fields of cell biology, oncology, immunology, gerontology, and neuroscience. The focus of this book is to provide an in depth analysis and provocative discussion of what role normal and aberrant proteasome function plays in regulating various aspects of brain homeostasis.