This document specifies the application of the time-of-flight diffraction (TOFD) technique to the semi-, or fully automated ultrasonic testing of fusion welded joints in metallic materials of minimum thickness 6 mm. It is primarily intended for use on full penetration welded joints of simple geometry in plates, pipes, and vessels, where both the weld and parent material are low alloyed carbon steel. Where specified and appropriate, TOFD may also be used on other types of materials that exhibit low ultrasonic attenuation (especially that due to scatter). Where material dependent ultrasonic parameters are specified in this document, they are based on steels having a sound velocity of (5920 ± 50) m/s for longitudinal waves, and (3255 ± 30) m/s for transverse waves. This has to be taken into account when examining materials with a different velocity. This document makes reference to the basic pre-standard ENV 583 6 and provides guidance on the specific capabilities and limitations of TOFD for the detection, location, sizing and characterisation of discontinuities in fusion welded joints. TOFD may be used as a stand-alone method or in combination with other NDT methods or techniques, both for manufacturing inspection (pre-service) and for in-service inspection. This document specifies four examination levels (A, B, C, D) corresponding to an increasing level of inspection reliability. Guidance on the selection of examination levels is provided. This document permits assessment of indications for acceptance purposes. This assessment is based on the evaluation of transmitted, reflected and diffracted ultrasonic signals within a generated TOFD image. This document does not include acceptance levels for discontinuities.