Abstract. Multiple Scattering (MS) theory, via the MXAN package, is able to reproduce the experimental XANES data of aqua ions, small molecules, and metal sites in biomolecules from the edge up to 150–200 eV. In this paper we present the last advances of the method, including the potential description and optimization. Improved parameterization also includes new routines to handle the structural determinants via generalized degrees of freedom. Examples will be presented to illustrate the method.