The International Atomic Energy Agency (IAEA) has sponsored a series of Coordinated Research Programs (CRPs) that have been focused on integrity of reactor pressure vessel (RPV) materials. The emphasis in the last few years has been on the development of a large fracture mechanics database of three-point bend fracture toughness tests on precracked Charpy specimens and larger 1T (25.4 mm thickness) compact tension specimens, using the Master Curve approach that has been standardized in ASTM Test Method for the Determination of Reference Temperature, To, for Ferritic Steels in the Transition Range (E 1921). More than 20 international laboratories have conducted a significant amount of fracture toughness testing to allow evaluation of the Master Curve results obtained following ASTM E 1921. The current CRP also has the objective to develop international guidelines for producing adequate Master Curve data and applying the data to RPV integrity analyses. This paper will first describe a preliminary review of the data that have been produced with emphasis on the A533B-1 correlation monitor heat JRQ, which has served as a key material for the CRP. The main emphasis of the paper will be on the development of international guidelines for applying the Master Curve data that can be obtained from irradiated sample material for the most limiting RPV material.