The oxidation ofa‐SiC single crystals and sintered α‐ and β‐SiC polycrystals has been investigated at elevated temperatures. Bubble formation is commonly observed in oxide scales on polycrystalline SiC but is rarely found on single‐crystal scales; bubbles result from the preferential oxidation of C inclusions, which are abundant in SiC polycrystals. The absence of bubbles on single crystals in fact implies that diffusion of the gaseous species formed on oxidation, CO (or possibly SiO), controls the rate of oxidati