The objectives of the work described in this WRC Bulletin were (1) to develop data on HAZ impact toughness and hardness under various metallurgical conditions@ including various vanadium and columbium contents@ low and high welding inputs@ and various PWHT conditions; (2) to identify the specific microstructural details that can lead to significant changes in the HAZ toughness and hardness@ especially the effects of vanadium and columbium additions@ welding heat inputs@ and PWHT; and (3) to investigate the fracture mechanism in a multipass HAZ@ including crack initiation and propagation@ and the mechanical and microstructural aspects controlling the fracture process. The investigation has led to a better understanding of the detrimental effect that the addition of microalloy vanadium and columbium has on the impact toughness of the multipass HAZ of C-Mn steels. Publication of this document - WRC Bulletin No. 395 was sponsored by the Pressure Vessel Research Council