[en] The existence of lead in steam generators, detected during analysis of deposits in the damaged areas of tubing and in the fracture surfaces of existing cracks, bears out the hypothesis that lead may contribute to the cracking problems arising in the tubing during operation. The lead present in a steam generator, which comes from the turbine, pumb seals, valve packing, liners etc, may form concentrations from 0,02% in the sludge. The fact that the lead comes from different sources limits the scope for controlling this contaminant and makes it difficult to reduce its concentration in the sludge below several hundred ppm. Taking these facts into account, it seems necessary to count on lead being present in new steam generators and to consider the influence of this contaminant on the behaviour of the materials considered as substitutes for Alloy 600. This paper presents the experimental work conducted with a view to determining the influence of the concentration of OPb in caustic environments and under AVT conditions, on the stress corrosion resistance of the nickel alloys used in the fabrication of steam generator tubing. Tests were performed at 320 degree centigree