A new program for refinement of layered structures is herein presented. FAULTS is based in the DIFFaX program, developed by Treacy et al. [1], which simulates selected area electron diffraction and powder (X-ray and neutrons) diffraction patterns by means of a recursion algorithm that calculates the incoherent sum of diffracted intensities of layered structures of any crystal system containing planar defects. In order to deal with the limitations of a simple simulation, refinement of all the parameters involved in the calculation of the diffracted intensities has been implemented in FAULTS.