Five percent chromium hot work tool steels have found application in the field of high strength steel design. A modification of Atlas Crovan was melted as an experimental 10-ton basic electric arc heat by Atlas Steels Limited, Welland, Ontario. The new material, designated as M-7-12, was, tested at the Physical Metallurgy Division, Mines Branch, to determine its mechanical properties, especially with regard to transverse ductility and response to various heat treatments. It was found that this steel exhibits excellent tensile strength consistent with good tensile ductility and good impact strength over a wide range of temperature. This alloy possesses an ultimate tensile strength of 275,000 psi at room temperature, and of 190,000 psi at 1000'F. The impact strength at room temperature is 25 ft-lb, and at minus 100°F, 15 ft-lb. These properties make the alloy one of the most outstanding of new high strength materials.