Non-dopedMg(x)Zn(1-x)O films (MgxZn1-xO films) and nitrogen-doped MgxZn1-xO films (MgxZn1-xO:N films) were grown epitaxially on Zn faces of ZnO single crystal substrates by the plasma-assisted reactive evaporation (PARE) method using ZnMg alloys. Optical parameters, refractive index n, extinction coefficient k, andabsorption coefficient a of these films and ZnO substratewere easily estimated by variable angle spectroscopic ellipsometry. The k values of these films abruptly increased with increase in photon energy near the absorption edge region. Dispersions of n of these films were sharper with larger peak values than that of a ZnO substrate. MgxZn1-xO films and MgxZn1-xO films:N films grown on a ZnO substrate by the PARE method are of high quality with less defects than those of a ZnO substrate. Maximumvalue of a of these films calculated fromk was about 2 x 10(5) cm(-1). The values of intercepts on photon energy h nu axis of (alpha h nu)(2)-h nu plots for these films and the ZnO substrate agreewith peak energy of PL spectra, the origin ofwhich is free excitons. These results indicate that absorption in those materials is dominated by exciton absorption. (C) 2014 Elsevier B.V. All rights reserved.