Hot cracking is a phenomenon occurring during welding. Hot cracks that form in the fusion zone are named solidification cracking while cracking that takes place in the heat affected zone is referred to as liquation cracking. This paper reviews the hot cracking phenomena specifically of relevance to austenitic stainless steels. The currently existing main theories explaining solidification and liquation cracking are considered together with the influence of main parameters in relation to susceptibility towards hot cracking. Important factors are the base metal microstructure, primary solidification mode, solidification rate, distribution of delta ferrite, amount of nitrogen, level of impurities and minor elements.