The work deals with the simulation of the direct billet-to-billet extrusion of alumin-ium alloys. The main task was to generate a model with finite elements to predict the interior failure length at the skidmark where the two billets are pressed together. This model should be used to determine the possibilities to decrease the interior failure length. Based on a FEM model of an industrial extrusion process built in Deform 2D™ the effect of the main influence parameters on the interior failure length were determined in parameter studies. In these studies the material flow at the pressing pad and the pre chamber geometry were found to have the most significant influence on the interior failure length. The work shows that it is possible to decrease the interior failure length about 20%. In additional studies new knowledge about construction of extrusion tools was gained. With improved tool geometry it is possible to increase the extrusion speed more than 30%.