Since the publication in 1998 of the last special issue of JGPN on the genetics of dementia, we have witnessed the completion of the Human Genome Project and an exponential increase in the identification of causative genes in human diseases. This special issue revisits the 6 neurodegenerative disorders described in that issue, offering important updates to the genetic findings for these disorders that together comprise the most common causes of dementia among elderly people. It is critical for practicing neurologists, psychiatrists, and geriatricians to keep abreast of these advances as they will impact the clinical diagnosis and management of these disorders. The reviews in this issue have been written by an outstanding group of international experts who provide a clear and insightful update on the molecular genetic advances and genetic counseling principles for each disorder.