Post-irradiation examination (PIE) is an indispensable step in the selection of new or improved research reactor fuel, and in the characterization and understanding of its in-core behaviour. This publication provides an introduction to PIE techniques. It describes a typical PIE process from intercycle inspections in the reactor pool or channel, to hot cell PIE, which is subdivided into non-destructive and destructive testing techniques with their typical output, advantages and drawbacks, and their applicability to understanding fuel irradiation behaviour. Much of the work presented in this publication originated from the research and development of new low enriched uranium research reactor fuels. Intended readers include research reactor operators, regulators and their technical support organizations, fuel developers and manufacturers, laboratory staff, and policy makers.