Standard optical coatings have been gamma irradiated in order to determinate their suitability for aerospace applications. Space environment was partially simulated through the employment of a Co-60 gamma (gamma) radiation source (total dose of 1 Mrad). A comparison between the different behavior under gamma-radiation conditions of TiO2 evaporated films and TiO2 sol-gel processed films is reported. The variations of the complex refractive index of films as result of the exposure to radiation have been measured by ellipsometry. Other optical properties (i.e. transmittance and wavefront distortion) are also reported in order to complete the comparison. (C) 2004 Elsevier B.V. All rights reserved.