Book excerpt: There is now considerable genetic evidence that the type 4 allele of the apolipoprotein E gene is a major susceptibility factor associated with late-onset Alzheimer's disease, the common form of the disease defined as starting after sixty years of age. The role of apolipoprotein E in normal brain metabolism and in the pathogenesis of Alzheimer's disease are new and exciting avenues of research. This book, written by the most outstanding scientists in this new filed, is the first presentation of results concerning the implications of apolipoprotein E on the genetics, cell biology, neuropathology, biochemistry, and therapeutic management of Alzheimer's disease.