Irradiation studies of Al2O3-, BeO, and pyrolytic-carbon-coated fuel particles have been carried out in the Battelle Research Reactor. Alumina-coated UO2 particles were found to be capable of a high degree of fission-gas retention during irradiations to at least 10 per cent bumup at temperatures up to 1100 C, The use of thick Al2O3 coatings (about 60 microns) and porous UO2 particles (about 80 per cent dense) was determined to be necessary to prevent cracking of the coatings at low temperatures. Coarse-grained beryllia coatings on UO2 particles have cracked during irradiations at 100 C and during thermal cycling in elevated temperature irradiations, but better performance is expected with fine-grained material. Failure of pyrolytic carbon coatings on UC2 particles was prevented in low-temperature irradiations by using thick coatings (>100 microns), but at elevated temperatures it was learned that the coatings had to be multilayered as well. Very promising results were obtained for pyrolytic-carbon-coated UO2 particles, good performance being observed over the temperature range of 100–1050 C.