The PbZr0.40Ti0.60O3/LaNiO3 multilayer thin films with different LaNiO3 film thickness were deposited on Pt/Ti/SiO2/Si substrates by a modified sol-gel technique. The optical properties of the PbZr0.40Ti0.60O3 thin films, LaNiO3 thin films, and the interface layers between them have been investigated using spectroscopic ellipsometry in the wavelength region of 400–1700 nm. For fitting the ellipsometric data to interpret the optical constants of the multilayer films, the unknown dielectric function of the PbZr0.40Ti0.60O3 films, LaNiO3 films, and the interface layers were constructed using a single-Lorentz oscillator. It is noted that the shapes of the optical constants are different for the three different layers because the fitted values of the model parameters are markedly different. It is found that the PbZr0.40Ti0.60O3 films are entirely transparent (namely the extinction coefficient κ=0) in the 400–1700 nm wavelength region. Moreover, the optical constants of the interface layer and the LaNiO3 films are focused on and discussed. © 2004 American Vacuum Society.