Structural integrity assessment codes and standards such as pressure vesselcodes PD 5500, ASME VIII and EN 13445; nuclear codes ASME III and RCC-M;DNV codes for offshore structures, and codes for fatigue design and the assessment of steel structures, BS 7608 and Eurocode 3, aim to ensure safe and fitfor-purpose structures through implementation of recognised best practice, backed up by theory, testing and experience. Codes and standards such as BS7910 and API RP 579-1/ASME FFS-1 also enable decisions to be made regarding continued fitness for service following defect initiation or cracking. Some codes and standards give very specific procedures for conducting structural integrity assessments with detailed guidance on the use of Finite Element Analysis (FEA) to determine stress/strain and distinct quantities such as limit load and stress intensity while others are more open ended and require the judgement of the practitioner to be used.