This article reviews the basic mechanisms of elevated-temperature behavior and associated design considerations with emphasis on metals. It discusses the key concepts of elevated-temperature design. These include plastic instability at elevated temperatures, deformation mechanisms and strain components associated with creep processes, stress and temperature dependence, fracture at elevated temperatures, and environmental effects. The article describes basic presentation and analysis methods for creep rupture. It provides information on the application of these methods to materials selection and the setting of basic design rules. The article discusses the limitations of high-temperature components, as well as the alternative design approaches and tests for most high-temperature components.