The X-ray crystal structures of selected aluminium compounds which may be of relevance to understanding aluminium binding in biological contexts are described. These fall into four main categories: (a) those complexes where the metal is in a mononuclear environment, as would be found in siderophore and similar chelating agent complexes, exemplified by the structures observed with oxygen donors and with N/O donors; (b) polynuclear aluminium complexes which are possibly important species in hydrolysing environments and relevant to aluminium uptake and bioavailability; (c) aluminium in environments found in metalloproteins; and (d) aluminium minerals relevant to bioavailability and to aluminium biomineralization and storage.