Interpretations of fracture toughness characteristics, as measured by various test procedures, are presented for structural aluminum alloys.Quantitative definitions of the significance of engineering fracture toughness tests are provided by extension of analytical procedures evolved from fracture mechanics theory.The procedural simplicity of the engineering tests, coupled with the analytical capabilities of fracture mechanics theory, provides for a significant advancement in fracture-safe design procedures for aluminum alloys covering the full range of yield strength.The interpretative procedures are evolved from correlations of KIc with the Dynamic Tear (DT) and Charpy V-notch test.An Optimum Material Trend Line (OMTL) diagram is developed which summarizes all the DT fracture toughness data and is additionally indexed according to the KIc and Cv correlation plots.