There have been great improvements in the quality of Al-27 NMR spectra from solids over the last decade. The impact of this technique on structure determination for a wide range of solids is briefly reviewed. Emphasis is placed on the effects arising from the presence of the quadrupolar interaction and strategies that allow unambiguous spectral interpretation. It is demonstrated that in addition to the chemical shift, the quadrupolar interaction itself can be a rich source of local information about solids. The insight obtained from Al-27 NMR into atomic level structure often contains surprises, such that previous models of structure and properties have to be reassessed.