ESDU 04019 presents endurance data for high-strength steels. The results of more than 10 000 constant-amplitude fatigue tests@ on plain and notched specimens subjected to rotating-bending@ plain-bending and axial loading@ are presented in the form of curves of alternating stress versus endurance. In the Data Item@ a high-strength steel is defined as a steel having a room-temperature 0.2 per cent proof stress greater than 800 MN/m2 (116 ?? 103 lbf/in2). The data presented relate to the medium and high-cycle regimes@ that is endurances of greater than 10 000 cycles. The data have been grouped according to type of steel based on the unified numbering system (UNS) codes and also according to alloy content@ the tempering temperature applied to the specimen before testing@ the test-piece shape@ the surface condition of the specimen and the size of the notch@ when present. Test temperature and mean stress are also considered. The text of the Data Item includes discussion of the data presented and of the influence of various factors on fatigue strength; the effects of tempering temperature@ mean stress@ test temperature and frequency@ loading type@ surface roughness and notches@ and surface treatment are all discussed in detail with reference to the data in the Item. Figures that illustrate explicitly the effects of some of these variables are also presented.