The major factor determining the fatigue life of a welded structure under a given loading is the configuration of the weldments. The selection of various steel types and welding processes are considered to be secondary influences on the fatigue strength. It is possible to improve the fatigue strength of weldments by a number of practical techniques. Research in progress indicates that the fatigue behavior of weldments can be predicted by the application of fracture mechanics theory; it is hoped that this will lead to a clearer understanding of fatigue and the development of more refined techniques of fatigue life calculation.