Alzheimer's disease (AD), the main cause of dementia, is characterized by the aggregation of amyloid-β (Aβ). This pathophysiological process starts many years to decades before the onset of clinical symptoms. Cerebrospinal fluid analysis and amyloid positron emission tomography scans are two standard methods to measure brain Aβ, but their invasive nature and expense limit their usage as screening tools. Therefore, peripheral Aβ studies have grown exponentially during the past few years. In this review, we discuss recent studies on plasma Aβ and its potential as a reliable biomarker of AD.