A procedure that makes use of a conventional stress value (ERS) is applied to spot welded joints. The ERS can be evaluated for every spot weld of the structural model. Through the use of ERS-N curves, fatigue data performed on different joint geometries can be successfully mixed together. One of the main aspects is that progressive damage deeply influences fatigue behaviour, so that a simple numerical solution neglecting accumulated damage is unable to foresee the whole fatigue life. In the present paper the method has been applied to many experimental results: it is shown that a unique criterion is able to deal with several different structures and materials.