The reflection spectroscopic ellipsometric study of optical properties of thin films of Al-Cr-Fe is presented. Glass substrates were used for the optical characterization of Al-Cr-Fe thin films. Polarizer, rotating polarizer spectroscopic ellipsometer (PRPSE) equipped with an achromatic quarter wave was used for thin films/glasses analysis. Al-Cr-Fe approximant thin films were deposited from the vapor phase on the glass substrates. The optical constants were determined at room temperature in the spectral range from 500 to 800 nm. The best glass/layer/Al2O3 model using for the regression procedure is validated by the transmittance technique. The refractive index and extinction coefficient vary with the wavelength from 3.8 to 5.3 and 4.3 to 3.5, respectively. Surface layer on the glass substrates was treated as a mixture of air and Al-Cr-Fe compound by using the Bruggeman effective medium approximation. The oxide thickness derived as an independent parameter in the best model is in agreement with the oxide thickness derived from X-ray photoelectron spectroscopy measurements. (C) 2003 Elsevier Science B.V. All rights reserved.