Interest in the use of nickel steels for low- and cryogenic-temperature applications has grown tremendously in the last decade@ especially for the containment@ processing and transporting of liquefied natural gases. Nickel has long had a reputation for enhancing both the strength and toughness of steels and its application in this field is recognized in ASTM Specifications A203@ A300 and A593@ which set compositions and toughness performance requirements for 2-1/4 and 3-1/2% nickel steels. At the present time@ these steels are used in the normalized condition@ and are limited in use to -90F for the 2-1/4% Ni grade (ASTM A203 Grade A) and -150F for the 3-1/2% Ni grade (ASTM A203 Grade D). Previous work had shown that accelerated cooling could enhance the toughness of these steels. If sufficient improvement in toughness could he gained by this treatment so that they could be used at temperatures 25-50F lower than their present limit@ it would be a valuable contribution to the application of the steels. It was the purpose of this study@ therefore@ to determine what improvement in toughness properties could be achieved for these steels by accelerated cooling.