A nationally coordinated materials development program for fast breeder reactors is being conducted to improve the economy and reliability of replaceable core components. The program is comprised of three parallel paths, including reference alloys for present applications, second-generation alloys for near-term applications, and third-generation alloys for longer term applications. Reference alloy work is complete, with the major program emphasis being placed on qualification of titanium-modified Type 316 stainless steel (D9) for core applications. Ferritic alloy, HT-9, has been identified as an excellent duct material, and qualification of this alloy is being phased in as D9 work is completed. Another four alloys have been identified as potential cladding materials and are scheduled for completed development and application by 1988.