Scope of Work A survey was made of the service experience of API-R tanks which included flat bottom carbon steel storage tanks operating below -20F. Information concerning the number and size of the tanks in service; the types of steels that were used for construction; the criteria used for fracture toughness; and the service experience of the owners was obtained. An analysis of the fracture toughness characteristics of the steels in the survey tanks and the service experience of the owners was made to establish whether a change in the criteria used in API-R should be considered. The structural integrity of other structures in carbon steels and their toughness requirements were reviewed and ranked. This study included pressure vessels@ oil tanks@ RR tank cars@ bridges and ships. The transfer of useful information from the experience of other structures to the material requirements of API-R tanks is discussed. The role that fracture mechanics can play and any additional information that needs to be developed to upgrade the material requirements in API-R is outlined.