The use of Laser Assisted Machining (LAM) can improve various aspects of the machinability of high strength materials. The laser is used as an intense heat source to decrease the strength of materials machined just prior to the cut. By modifying certain parameters such as power, position of the beam, cutting parameters, the machinability and/or the microstructure of the surface layer are often modified by the beat input from the laser. A study was undertaken to determine the optimum cutting parameters and to quantify their influence on the fatigue strength and depending on the type of microstructure created in two metals: a bearing steel (100Cr6/AISI 52100) and an aeronautical titanium alloy (Ti6Al4V). In the bearing steel a significant increase in the fatigue resistance was observed due to the transformation of the surface layer into martensite. In the titanium alloy, a slight reduction in the fatigue strength was found as in this case the microstructure and residual stress state of the surface layer were less beneficial. The surface roughness was also measured and no significant variation was observed for different laser powers in each material.