A large volume of data concerning the 2 1/4, 3 1/2, 5, and 9% nickel steels, corresponding to ASTM specifications A203 Grades A and D, A353, A553 Type I, and A645, has been collected from open literature and private sources.The mechanical-property data collected includes tensile-test properties at ambient and cryogenic temperatures, notch toughness, fracture toughness, and fatigue strength.A brief description of each of the testing methods used and their significance to cryogenic service are included. Tables and figures summarizing the data are presented.The strengths and toughnesses required by the respective ASTM steel specifications and ASTM specification A593 are normally met or exceeded by the steels.For the lower nickel steels, gains in toughness can be obtained by quenching and tempering rather than normalizing.