Oxide dispersion strengthened (ODS) steel cladding on mixed-oxide fuel pins offers high-temperature strength and creep rupture resistance properties for a long-life fast reactor. The fabrication and irradiation of the large diameter ODS steel cladding with high-density mixed-oxide pellets were performed at the Argonne National Laboratory Experimental Breeder Reactor II. Two developmental ODS alloys and two fuel-pin designs were used in this study. The tests were continually monitored during irradiation followed by nondestructive and destructive examinations. Both designs were successful and demonstrated the potential of ODS steel as a cladding material.