WRC Bulletins 457, 458 and 459 form an integral set documenting the development of an alternative to the ASME Section III RTNDT procedure based on To, and the development of an ASME Code Case. The three bulletins should be purchased as a set. WRC Bulletin 457 Fracture Toughness of Ferritic Steels and ASTM Reference Temperature (To), describes the results of the three-phase project initiated by the Committee on Failure Modes of Components of the Pressure Vessel Research Council: 1. To verify the Master Curve approach for pressure vessel steels, 2. to develop a database which can be used in the future development of ASME Boiler and Pressure Vessel Code procedures which make use of To or the Master Curve approach and 3. To use the data to develop and verify an ASME Code Case. A proposed ASME Code Case is presented which uses the current KIc curve, but is shifted using an equivalent reference temperature, which is based on the fracture toughness reference temperature, to, rather than the RTNDT value based on Charpy impact and drop weight test results. Two separate Code Cases based on the proposed draft have been approved by the ASME Boiler and Pressure Vessel Code -- Code Cases N-629 and N-631 for Section XI and Section III applications, respectively.