Liquation cracking can occur during fabrication by welding in either the heat affected zone in the parent material, or in previously deposited weld metal during a subsequent run. It results from localized melting at grain or other boundaries, combined with the thermal strains associated with welding. This review paper opens with brief descriptions of the classification, identification and mechanisms of liquation cracking. Following an outline of the material classes and circumstances in which it is most likely to occur, compositional influences in austenitic stainless steels and nickel alloys are considered in more detail. It is emphasized that although residual elements such as S, P or B may have an important role in causing or enhancing liquation effects, much liquation cracking is associated with intentional minor alloying additions, such as Nb. The influence of deliberate alloying additions, and compositional balance, in limiting the influence of residuals will be considered. In conclusion the detection, significance and avoidance of liquation cracking are discussed briefly.