This study was carried out under the direction of Dr. Peter St George-Hyslop and Dr Rogaeva at the Tanz Centre for Research in Neurodegenerative Diseases (CRND), University of Toronto. In order to explore the potential role of hereditary factors, a registry at the Tanz CRND with a coordinator was established for families in which two or more individuals have the suspected diagnosis of Alzheimer’s Disease or other forms of dementia. Eligibility requirements were disseminated through the CRND website. Individuals who contacted the Registry received a family history questionnaire in the mail. For sufficiently informative families, researchers sought consent to obtain blood samples from available family members required for genetic research. Collaborating neurologists and genetic counselors also referred families that fit the requirements. All collected individuals were given numeric IDs to protect their privacy. Families were eligible if: two or more members, living or decease, were affected by Alzheimer’s Disease, Parkinson’s Disease, amyotrophic lateral sclerosis, frontal temporal dementia or Creutzfeldt-Jacob Disease. Families were ineligible if: there were fewer than 2 affected members or family history was unavailable to document.