The flank breakage of gears is a failure mode that is separate from the damage forms such as root breaking or pitting. Consequently, it adds a further risk factor for gearbox failure. To be able to calculate this damage form in advance, extensive studies were performed on spiral bevel gears by Dr. Annast at the FZG Munich. On the basis of this analysis, the flank breakage calculation for bevel gears, and additionally for cylindrical gears, was implemented in the current Kisssoft Release 03/2011 (module ZZ4). Thus, a reliable risk assessment of flank breakage and its calculation is now available for the user.