Of the several factors tending toward failure of fuel-particle coatings in irradiation, fuel swelling and radiation damage to the first 15–20 μm of coating by fission recoils are concluded to- deserve the greatest immediate attention. Whereas ceramic coatings of sufficient thickness might withstand the stress, thinner coatings containing cushion layers or voids can be designed in principle to accommodate the effects of radiation damage. This has been demonstrated for pyrolytic carbon and alumina coatings formed by chemical vapor-deposition reactions. These principles cannot be applied to oriented coatings whose grains suffer anisotropic radiation damage by neutrons. This factor may ultimately limit the applicability of BeO coatings. Crushing strength, density, and hardness data are presented which show that pyrolytic carbon coatings with the same microstructure can have a wide range of properties. It is concluded that pyrolytic carbon coatings are not properly characterized by the terms ‘laminar’ and ‘columnar’ frequently used to describe their appearance. In the case of Al and Be coatings obtained by hydrolysis of the respective chloride vapors, deposition temperature is the most significant factor determining grain structure and permeability. A12O3 coatings range from porous amorphous varieties, through an impermeable ‘glass’ to elongated grains extending through the coating. The equivalent of the Al2O3 glass has not been observed in the BeO coatings. MgO coatings can be expected to be of limited utility because of low strength. ZrO2 coatings have the deficiency of permitting rapid oxygen diffusion.