Results are presented of a study of the inverse problem of ellipsometry. In the lack of inverse equations, iterative methods (search) are needed to find the optimal parameters (global minimum) of the adaptive optical model. Different kinds of optical models and search strategies are demonstrated and compared for evaluating real ellipsometric measurements. It is also demonstrated that the well-known gradient search alone is useless if the search space is large (few a-priori information) or the error surface is hilly The applied algorithms were built in a software, which is freely available at [email protected]. (C) 2003 Elsevier B.V. All rights reserved.