Occurrence rates of dementia are expected to rise alarmingly over the next twenty years. This issue of Neurologic Clinics reviews the leading dementias and explores epidemiology, etiology, differential diagnosis, and existing pharmacotherapies. Articles included are:: The Genetics of FTD (Wszolek); FTD (Josephs); An Update on the Amyloid Hypothesis (Eckman); Animal Models and Dementia (Hutton); Neuroimaging and Dementia (Jack); The Genetics of Alzheimers Disease (Taner); MCI/AD (Petersen); Vascular Dementia (Chui); Normal Pressure Hydrocephalus (Graff-Radford); Lewy Body Disease (Ferman); Parkinsonian Related Dementias (Boeve); Prion Disease (Eggenberger); and Assessment of Rapidly Progressive Dementia (Geschwind).