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Cyclic loading causes fatigue cracking in a ship's welded structural details. If these are not designed to resist fatigue cracking, the ship's profitability may be affected by repair costs and its economic life shortened. Fatigue cracks also may lead to fractures in the ship's primary hull structure, resulting in catastrophic failure. It is therefore necessary that structural designers use techniques that will minimize fatigue damage, ensuring structural integrity for the ship's intended service life. One such technique uses empirical data derived from laboratory tests of representative structural details. Data resulting from fatigue tests are presented in terms of stress applied to each detail and the number of cycles required to reach failure, commonly referred to as S-N curves. This WRC Bulletin presents S-N curves, developed from an extensive database, for typical welded structural details; the data are presented in graphs and tables as well. Publication of this document - WRC Bulletin No. 398 was sponsored by the Welding Research Council; the research work was sponsored by the Ship Structure Committee, An Interagency Advisory Committee (Secretariat: U.S. Coast Guard) and also is available as SSC Report No. 369