A series of six wide-plate crack-arrest tests was recently completed by the Heavy-Section Steel Technology program at the National Bureau of Standards, Gaithersburg, MD, using tensile-loaded specimens of A533 Grade B Class 1 steel. Crack-arrest data were obtained at temperatures in the transition range and above the onset of the Charpy upper shelf, thereby providing a basis for the development and evaluation of improved fracture-analysis methods. The 1 by 1 by 0.102-m single-edge-notched (SEN) specimens were welded to long straight pull tabs and subjected to a transverse linear temperature gradient before loading. The crack tips were sharpened by hydrogen-charging an electron-beam weld. The tests were designed to obtain crack arrest near the middle of the specimen where the temperature would produce a high-toughness level in the upper transition region of the material. The specimens were instrumented with strain gages and thermocouples. Initial static design calculations were made using textbook formulas. Additional calculations, using an assumed set of K_ID versus ˙a and T relations and an effective stress wave concept, confirmed the reasonableness of tentative design parameters. Pretest and posttest dynamic finite-element calculations were performed for each test. Computed results are compared with transient data for crack-line strains, crack speed, crack-opening displacement, arrest location, and postarrest tearing. Results from both application-mode and generation-mode dynamic analyses are presented. The arrest toughness values calculated from the test data are summarized for temperatures ranging from the transition into the Charpy upper-shelf range.