Phase modulated spectroscopic ellipsometry has been used to characterise electron-beam evaporated Gd2O3 films deposited on quartz substrates. The ellipsometric measurements have been done in the wavelength regime of 300-1200 nm and the experimental ellipsometric data have been fitted with theoretical spectra generated assuming a realistic sample structure. The optical constants of the substrate have been supplied and for the optical constants of Gd2O3, two different dispersion relations, viz., the dispersion relation proposed by Forouhi and Bloomer (FB) and the Tauc-Lorentz (TL) dispersion relation proposed by Jellison and Modine have been used. The best fit sample structures and the values of the optical constants of the Gd2O3 films determined using the two different models have been compared. It has been observed that though the refractive index values obtained by using the two models are similar, only the TL model could estimate the band gap of the films correctly. (C) 2004 Elsevier B.V. All rights reserved.