Abstract: This is a process for improving the fatigue properties of structures which have dislocations or deformed regions in the surface layers. Solute is diffused into this surface region and inhibits the atomic movements which lead to initiation and growth of fatigue cracks. The deformed regions can be produced by pre-cyclic straining of the structures. The process is applicable to metals and crystallographic mterial that are susceptible to fatigue failure. Moreover, cyclic straining of polymers and glasses will produce defect structures in the surface layers and solute diffused, as in the case of above, will also impede further development of defects and reduce the susceptibility of the structure or object of fatigue failure.