This special issue of Disasters examines what one may call ‘the social life of humanitarian action’. It deals with questions of how humanitarian action is shaped in practice and how it affects the societies where it is implemented. The articles constitute a selection of more than 450 papers presented at the first World Conference of Humanitarian Studies (WCHS), held in Groningen, The Netherlands, in February 2009, which was the first conference of its kind to explore the growing field of humanitarian studies that examines how humanitarian crises evolve, how they affect people, institutions and societies, and the responses that they trigger. The issue distinguishes three dimensions of the social life of humanitarian action: first, the normative dimension where humanitarian action draws on different sets of principles and objectives, which often clash in practice; second, the complex processes that shape humanitarian action in everyday practice; and third, the ways in which it affects society at large, changing people’s outlooks, altering power constellations, transforming institutions and leaving footprints on spatial organisation.