A brief review is presented of the development and evaluation of coated-particle fuel for the Peach Bottom high-temperature gas-cooled reactor. The results of extensive thermal and irradiation tests on the Peach Bottom fuel materials have shown them to be adequate for a 3-yr core life of this reactor. Consideration of the mechanisms that could lead to coating failure under irradiation has shown that swelling of the carbide particle from fission-product accumulation and shrinkage of the pyrolytic-carbon coating from fast-neutron and fission-recoil effects are the principal contributors to coating failure. A “Triplex” pyrolytic-carbon coating has been developed to overcome these effects. This coating consists of a spongy layer of pyrolytic carbon overcoated with successive layers of laminar and columnar pyrolytic carbon.