Alzheimer's disease (AD) is most prevalent cause of dementia and no cure has been discovered. Although the framework of AD clinical trials is being established utilizing results of large-scale observational studies such as the AD Neuroimaging Initiative (ADNI) and the Japanese-ADNI (J-ADNI), the development of disease-modifying therapy for Alzheimer's disease (AD) has not yet been achieved. Preclinical AD was recently defined as a new disease stage in which AD is asymptomatic but biomarkers suggest the presence of amyloid pathology. Preclinical AD has been focused as promising therapeutic time window and establishment of reliable biomarkers for preclinical AD is an urgent task. The Japanese Agency for Medical Research and Development (AMED) preclinical study is a nationwide multicenter observational study carried out by public research funding from AMED as a successor to the J-ADNI study. The goal of this study is to establish a biomarker that can quantitatively evaluate the disease progression of preclinical AD and mild cognitive impairment (MCI) or predict the progression to MCI and dementia in the future. To achieve this goal, the following assessments will be conducted over time for three years: clinical evaluations; cognitive tests; genetic testing; body fluid biomarker tests; and imaging biomarker studies such as MRI, FDG-PET, and amyloid PET. The obtained data will eventually be released to the public database.