As the automotive industry seeks to remove weight from vehicle chasses to meet increased fuel economy standards, it is increasingly turning to composites and aluminum. In spite of increasing demands for quality aluminum alloy spot welds that enable more fuel efficient automobiles, fatigue evaluation procedures for such welds are not well-established.This article discusses the results of an evaluation Battelle performed of the fatigue characteristics of aluminum alloy spot welds based on experimental data and observations from the literature. In comparison with spot welds in steel alloys, aluminum alloy spot welds exhibit several significant differences including a different hardness distribution at and around the weld, different fatigue failure modes, and more.The effectiveness and applicability of the Battelle structural stress-based simplified procedure for modeling and simulating automotive spot welds has previously been demonstrated by Battelle investigations. After considering the fatigue characteristics of aluminum alloy spot welds, it was concluded that the Battelle structural stress-based simplified procedure and the master S-N curve approach based on this procedure were adaptable to aluminum spot welds.Battelle researchers used structural stress-based simplified procedure to compare available fatigue data for spot welds in aluminum alloys were with the existing master S-N fatigue curve for welded aluminum alloys. The existing curve contained data for numerous fusion and friction-stir welds. The comparison clearly showed that the weld procedure did not significantly affect the fatigue life of good quality welds, and that a single master S-N curve was possible for spot, fusion and friction-stir welds in the aluminum alloys considered, when the equivalent Battelle structural stress range was used.