The lecture presents methods of evaluating degradation processes in structural materials. Attention is focused primarily on the analysis of microstructural conditions for the initiation of brittle and ductile fracture, fatigue damage, creep, corrosion damage, stress corrosion cracking, and basic mechanisms of wear on functional surfaces. This analysis is followed by an explanation of the influence of temperature, loading mode and environmental parameters on the initiation of limit states - leading to fracture and the loss of the basic material function, i.e. transfer of the stress-strain field. Methods for evaluating these degradation processes are applied to metals, ceramic materials, polymers and basic types of composite materials. Particular attention is focused on the influence of the size and shape of structural components on the initiation of limit states and methods for assessing the resistance of structural components exposed to the negative effects of degradation processes. The lecture concludes with a presentation of methods for risk estimation of structures – both during the design stage and as part of operational decision-making during service life.