This issue of Acta Neuropathologica includes a cluster of three review papers focusing on amyloid β-peptide (Aβ) and/or τ-protein aggregates in Alzheimer’s disease (AD). Since the first description of the disease by Alzheimer [1], Aβ-containing amyloid plaques and τ-derived neurofibrillary tangles (NFTs) have been identified to represent the pathological hallmarks of AD [1, 6, 8]. These two types of protein aggregates share a number of biochemical features. Both form fibrils, which are the major compounds of amyloid plaques (Aβ fibrils) and neurofibrillary tangles (τ fibrils; NFTs). Both proteins were shown to undergo posttranslational modifications, such as phosphorylation, truncation and/or pyroglutamate formation in the AD brain. These modifications may accelerate the speed of aggregation in vitro. Moreover, Aβ has been shown to promote τ aggregation [5, 7], suggesting that protein aggregation represents a key starter and/or promoter of the disease. The ability of Aβ to functionally interact with τ may depend on other proteins such as N-methyl-d-aspartate (NMDA) receptors that act as molecular switches to induce neuronal dysfunction and neurodegeneration. Figure 1 provides a schematic representation of the roles of Aβ and τ as presented in this cluster. The clinical manifestation of AD is, thereby, associated with high levels of mature Aβ and τ aggregates widely distributed throughout the brain.