The inelastic neutron scattering spectrum of crystalline azulene has been measured and compared with the results of isolated molecule ab initio and periodic DFT calculations. The comparison infers that the molecular geometry in the solid state retains the C-2v symmetry, and likely the geometry, of the isolated molecule. The disordered nature of crystalline azulene which prevents determination of molecular structure is investigated by consideration of two limiting packing arrangements. (c) 2007 Elsevier B.V. All rights reserved.