Alloys intended for use in high-temperature environments rely on the formation of a continuous, compact, slow-growing oxide layer for oxidation and hot corrosion resistance. This article focuses on the issues related to high-temperature oxidation of superalloys used in gas turbine engine applications. It discusses general methodologies to evaluate oxidation resistance of materials. The article describes the performance characteristics of superalloys, single-crystal superalloys and other high-temperature materials such as refractory metals and ceramics. It discusses hot corrosion of superalloys and airfoil degradation due to deposits resulting from ingested particles or sand. The article concludes with a discussion on the limitations of testing techniques and life prediction.