The misfolding, aggregation and accumulation of proteins in the brain, represents a common feature of diverse neurodegenerative diseases among which Alzheimer’s disease (AD). Important therapeutic strategies for this pathology aim at inhibiting the aggregation of misfolded amyloid β (αβ) peptides into different species, particularly intermediate oligomeric assemblies, which are believed to be the most neurotoxic species. Here we review the structural data present in the literature, with the purpose to supply useful information for the rational design of new potential molecules able to target αβ peptides and fibrils. In particular, structural information concerning the different αβ peptides assemblies, their supramolecular organization, their interaction with cations, biological membranes and known ligands are reported.