Abstract Metallic fuels were the first fuels chosen for liquid metal cooled fast reactors (LMRs). In the late 1960s worldwide interest turned toward ceramic LMR fuels before the full potential of metallic fuel was realized. However, during the 1970s the performance limitations of metallic fuel were resolved in order to achieve a high plant factor at the Argonne National Laboratory's Experimental Breeder Reactor II. The 1980s spawned renewed interest in metallic fuel when the Integral Fast Reactor (IFR) concept emerged at Argonne National Laboratory. A fuel performance demonstration program was put into place to obtain the data needed for the eventual licensing of metallic fuel. This paper will summarize the results of the irradiation program carried out since 1985.