This report discusses the results of a research program on the fatigue behavior of sound weldments in thick aluminum alloys.The specimens of alloy 5083-0 were provided by three aluminum companies and included plain plates, longitudinally welded plates, and transversely welded plates.Axial fatigue tests were conducted on 54 specimens.The results are shown in S-N diagrams.In addition, a supplemental test program was conducted.This program included the study of residual stresses, weld geometry, and weld quality.