Abstract Purpose of this paper is the presentation of the techniques used in fatigue life forecasts for a submarine pipeline, which have been worked out during the design of the Tran Mediterranean Pipeline. The stress level imposed by supports configuration, pipeline weight, weight-pressure-temperature of the internal fluid, is further increased by cyclic loads of sensible extent, resulting from hydro elastic phenomena of interaction between spanning pipe and sea bottom currents; the synchronization between the characteristic frequencies Forte-shedding and the natural frequencies of the spans provokes cyclic loading which affect negatively the fatigue life of the pipeline. The model proposed for fatigue analysis based on the fracture mechanics theory for which experimental tests have been required to determine the crack growth rate versus the variation of the stress intensity factor. Tests have been carried out on the base metal and in the heat affected zone, both in air and in sea water with catholic protection. In order to check the hypotheses and to determine the value to be assigned to the initial defect, full scale tests have been carried out on pipe lengths containing the circumferential weld and the related S-N curves have been plotted. Both deterministic and probabilistic approaches have been followed. According to the deterministic model, it has been found that the selection made of the parameters of the Paris law (Co, n) and of the value assigned to the initial defector(ai) led to conservative results with respect to the breakages of the experimental tests. On the contrary, the probabilistic model has been used in sensitivity analysis in order to establish the influence that each parameter had in the determination of the fatigue life. The results of this research have affected the design choices from. the operations of route selection; in particular, they were among at the determination of the intervention works on the sea hot tom before pipe laying, and the possible installation of overweight or pipe supports in order to avoid free spans of unacceptable length, and at the determination of the interval between periodic inspections. Introduction One of the problems to be dealt with in designing a sea line is the fatigue caused by vortex shedding on the free spans that are present when the sea line is installed on the sea bottom, or those generated by the relative movement between the pipe and the sea bottom during operations. In order to solve such a problem, the following must be known:both the static and dynamic stress states;the fatigue behavior of the material;the distribution of defects that can induce fatigue cracks. In order to calculate static stress under various conditions (empty pipe, operating conditions), we need to know both the profile of the pipeline with respect to that of the sea bottom, and the residual pulling force left by laying operations, which varies from one site to another. Such data are continuously recorded during laying operations and thus a complete knowledge of the initial conditions of pipeline is obtained.