This publication provides an overview of the status of post-irradiation examination (PIE) techniques for water reactor fuel assemblies and their components with emphasis given to advanced PIE techniques applied to high burnup fuel. The progress made in non-destructive and destructive PIE techniques used for investigation of water reactor fuel is described. Recent practice in high burnup fuel investigation revealed the importance of advanced PIE techniques, such as 3-D tomography, secondary ion mass spectrometry, laser flash, high resolution transmission, scanning electron microscopy, and image analysis in microstructural studies, for understanding mechanisms of fuel behaviour under irradiation. The importance and needs for in-pile irradiation of samples and rodlets in instrumented rigs were also discussed.