The original BioFINDER 1 cohort started to include participants in 2008. Since then there has been a rapid development of biochemical and neuroimaging technologies which enable novel ways to the study biological processes involved in Alzheimer's disease in living people. There has also been a growing interest in the earliest stages of AD and other neurodegenerative diseases. With the advent of new tau-PET tracers there is now an opportunity to elucidate the role of tau pathology in the pathogenesis of AD and other tauopathies. The Swedish BioFINDER 2 study has been designed to complement the BioFINDER 1 study and to e.g. address issues regarding the role of tau pathology in different dementias and in preclinical stages of different dementia diseases. Further, the clinical assessments and MRI methods have been further optimized compared to BioFINDER 1.