This monograph presentsapproaches to characterize inelastic behavior of materials and structures athigh temperature. Starting from experimental observations, it discusses basicfeatures of inelastic phenomena including creep, plasticity, relaxation, lowcycle and thermal fatigue. The authors formulate constitutive equations to describe the inelastic responsefor the given states of stress and microstructure. They introduce evolutionequations to capture hardening, recovery, softening, ageing and damage processes. Principles of continuum mechanics and thermodynamics are presented to provide aframework for the modeling materials behavior with the aim of structuralanalysis of high-temperature engineering components.