The potential of the Friction Stir Welding (FSW) process is easily observed in the creation of defect free welds in almost all of the Aluminum alloys. The success and applicability of the process, however, will depend on the performance of the welds compared to other joining processes. Experimental testing and evaluation are necessary for the determination of the mechanical response of Friction Stir Welds and vital to the development and optimization of the FSW process. The goal of this experimental testing of Friction Stir Welds is to obtain the data necessary to begin understanding the effects of the FSW process. An attempt has been made to systematically examine the effects of FSW process parameters and alloy on the weld properties. An attempt has been made to evaluate and compare High Speed and Low Speed Friction Stir Welds.