This Part of BS 3518 recommends the general principles to be followed in conducting fatigue tests on metallic materials. It gives definitions of recommended terms, guidance on the planning of the tests, and describes effective methods for the graphical presentation of the results. The forms of fatigue testing considered encompass both the use of uncracked and precracked test pieces; the former under either stress or strain control, and the latter under stress control and within the limits imposed by linear elastic fracture mechanics. The general principles are presented initially in terms of the fatigue testing of plain test pieces under a constant amplitude loading in a normal laboratory environment. Subsequently the general principles are extended to include additional concepts and recommendations associated with the testing of notched test pieces or structural components, testing in different environments and testing under variable amplitude loadings. Welded test pieces are not covered.