A method for the determination of optimal tooth modifications in spiral bevel gears based on load distribution@ minimized tooth root stresses@ and reduced transmission errors is presented. Modifications are introduced into the pinion tooth surface considering the bending and shearing deflections of gear teeth@ local contact deformations of mating surfaces@ gear body bending and torsion@ deflections of the supporting shafts@ and manufacturing and alignment of mating members. By applying a set of machine tool setting parameters@ the maximum tooth contact pressure can be reduced by 5.4%@ the tooth fillet stresses in the pinion by 8% and the angular position error of the driven gear by 48%@ based on a spiral bevel gear pair manufactured by machine tool settings determined by a commonly used method.