Fatigue tests on a parallel-wire large-diameter cable system for cable-stayed bridges and a detailed review of other fatigue test results are conducted. As a result, it is made clear that as the diameter of a cable increases, its fatigue strength decreases, stress concentration at the cable anchor portion is the principal factor influencing the fatigue strength of large-diameter cables within working stress range in fatigue design of cables, and when the cable is grouted with cement for anticorrosion purposes, nongalvanized wires may have their life extremely shortened by corrosion fatigue due to excess water after a chemical reaction, which depends on the quality of material and on the manner of execution. Furthermore, the design S-N curves, which are based on 5% wire breakage life, are proposed. The results of this study are used for fatigue design of Honshu-Shikoku railway/highway cable-stayed bridges which are constructed over the sea (severely affecting durability), and on which a large repeated load due to railway acts.