A method for the re-ana1ysis of test data of structural stecI components under cyclic actions is presented in this paper. The method is based on an S – N line (i.e. stress range-fatigue endurance line) approach and, althougb proposed here for low~c1e fatigue, was derived and is valid also for high cycle fatigue. A statistical approach for the assessment of the S – N lines, which is based on a selected probability of failure with reference to suitable levels of safety and reliability of the structural elements, is presented. Possible definitions of parameter S, as well as, failure criteria for the appraisal of N, are compared and their influence on the value of the slope of the S – N line is discussed. Finally, a design approach is proposed, based on a direct assessment of the cumulative damage in steel components under variable amplitude loading histories. In order to validate and to analyse its accuracy, test data of beams, beam-colunms and beam-to-colunm connections under cyclic and/or variable amplitode loading histories have been considered.