Deep geometry of two reverse faults, that originate monoclinal folds on the overlaying sedimentary cover, has been carried out from mapping and field data in the Sepulveda area (Spanish Central System northern border). Two NNW-SSE geological cross-sections, perpendicular to the general strike of the structures (E-W), have been constructed. By means of surface data (dip and strike) and fold geometry (dip limbs, interlimb angle, etc.) different fault-propagation fold models have been applied. These models allow to determine the deep geometry of the reverse fault that originate the observed folds. Different methods provide similar solutions, showing a 35° S dip value for the fault related to the Sepulveda fold and a 55° S dip value in a northern reverse fault