Progressive accumulation of amyloid plaques in the brain is a characteristic pathological change in Alzheimer's disease (AD) and precedes the presentation of cognitive impairment. In vivo detection of amyloid deposits using molecular imaging technique would thus prove useful for early diagnosis of AD and tracking disease progression. Several imaging agents have been developed that can noninvasively detect amyloid plaques in the brain and successfully differentiated AD patients from healthy normal individuals using positron emission tomography. Although validation remains required as to whether retention of these agents in the neocortex truly reflects the level of amyloid deposition, such findings suggest the potential usefulness of amyloid imaging technique for early diagnosis of AD.