Abstract Alzheimer's disease (AD) is a complex neurodegenerative disorder of which the exact cause is still not known. There has, however, been remarkable progress in the understanding of the pathophysiological events that underlie the disease with a focus on amyloid formation. We do not know yet if amyloid is the most crucial target for an effective therapy in AD. The new amyloid PET imaging tracer ligands offer possibilities for measuring fibrillar beta amyloid (Aβ) in the brain and for studying the time course of amyloid in the brain. This opens up new possibilities for early diagnosis as well as new tools for monitoring anti-amyloid therapy in AD.