During laser cutting of relatively thick workpieces the erosion takes place at a nearly vertical plane at the momentary end of the cut. That plane is covered by a thin molten layer, that is heated by absorbed laser radiation and by reaction. The removal of material from that layer is carried out by evaporation and by ejection of molten material due to the friction between the melt and the reactive gas flow. A computer simulation of that model yields a more detailed understanding of laser cutting and agrees well with experimental investigations.