The local structure of tris(8-hydroxyquinoline) aluminum(III) (Alq(3)) in three different crystalline poly-morphs, alpha-, gamma-, and delta-Alq(3), and amorphous Alq(3), are investigated by Al-27 NMR experiments, which include two-dimensional multi-quantum magic-angle spinning (MQMAS) experiments and one-dimensional variable B-0 field MAS experiments. The quadrupolar and chemical shift parameters of these Alq(3) samples are determined, including the distributions. These parameters reflect the local structure of respective samples and it is found that the gamma- and delta-Alq(3) consist of the facial isomer with well-defined crystal structure, whereas the alpha- and amorphous Alq(3) consist of the meridional isomer with distributions of quadrupolar coupling constants. It is also found that two distinct components exist in alpha-Alq(3). (C) 2009 Elsevier B.V. All rights reserved.