This handbook has been compiled by the Working Group "Ultrasonic Testing of Austenitic Welds" of the International Institute of Welding, IIW - Commission V (NDT and Quality Assurance), Sub-commission VC, Ultrasonic-Based Weld Inspection Topics. This is the second edition of the handbook which was first published in 1986. Since then, there has been some progress in understanding the underlying difficulties associated with the detection and the sizing of flaws in austenitic weld metal and this is included in this edition. In addition, the scope of the second edition has been increased to include: - Inspection of dissimilar-metal welds and duplex materials - in-service inspection - the common types of flaws which occur during fabrication and service in austenitic welds, and - the benefit to be derived from the use of horizontally polarized shear waves for the inspection of columnar grained material. Apart from the first edition, this handbook has been based on a similar handbook published in 1994 on the ultrasonic inspection of cladding and clad components. The theoretical aspects of ultrasonic propagation in austenitic weld metal are similar to those described for cladding in the cladding handbook. This handbook covers the ultrasonic inspection of austenitic butt welds. However, the guidelines and recommendations are relevant to welds of most configurations. The objective of the handbook is to inform all those involved in the volumetric examination of austenitic welds of the limitations caused by the acoustic properties of the material. The handbook is intended to provide guidance for the preparation of procedures for specific applications, but does not provide a detailed inspection procedure for any particular weld. The handbook is addressed to technicians, engineers and scientists involved in austenitic weld inspection. It should be of particular value to those responsible for preparing inspection procedures.