Abstract: Alzheimer's disease (AD) is the most common form of dementia, the pathological features of AD include neuritic plaques composed of beta-amyloid protein, neurofibrillary tangles. Direct imaging of amyloid load in patients with AD in vivo would be useful for the early diagnosis of AD and the development and assessment of new treatment strategies. Different strategies are being used to develop compounds suitable for in vivo imaging of amyloid deposits in human brains. Two compounds, ¹⁸F-FDDNP and ¹¹C-PIB, both show more binding in the brains of patients with AD than in those of healthy people. Additional compounds will probably be developed that are suitable not only for PET but also for single photon emission CT (SPECT).