The fatigue loading for the mooring and riser supports are often produced by a mooring/riser designer. Besides, the low frequency component may be significant for example in the moor-ing fatigue loads whereas the hull girder stress response is typically dominated by the 1st order wave loads. Close to the mean water line the stress responses become non-linear due to the effect of intermittent wet and dry surfaces. Accounting for this effect can be done by introducing corrections for the external pressure distributions at the cost of additionally complicating the analysis procedure. Several of the fatigue critical FPSO (floating production storage offloading) details are loaded by two simultaneous load processes. Examples being all foundations loaded by the external support loads and the global hull girder loads. For some structures also the wind loads are relevant for fatigue and their effect needs to be combined with that of the wave loads. In most cases the fatigue damages for the two loads are analyzed separately. There is seldom sufficient data on the actual stress response spectra to support accurate combining the responses for damage analysis.