Waders are among the most characteristic birds breeding in Arctic regions. The group includes species such as the Knot Calidris canutus and Turnstone Arenaria interpres whose breeding distribution spreads to the. most northerly points of land in the world, along the shores of Greenland and Ellesmere Island bordering the Arctic Ocean. To succeed, these species must be highly adapted to their environment, able to fit all the events of the nesting season—territorial procurement, laying, incubation and hatching of eggs, and raising of young—into the short Arctic summer, able to withstand extremes of weather and fluctuations in food supply, and to avoid the attentions of mammalian and avian predators. To exploit their Arctic niche, these birds make long and spectacular migrations from a wintering area where climate and food supply are suitable for subsistence but not for reproduction. Owing to the remoteness of the Arctic breeding areas, details of the migrations of these species have remained obscure or undocumented until relatively recently. This article describes the development of research on wader migration in Britain and the research expeditions which have taken place since 1970 to various Arctic, sub-Arctic (and sub-tropical) areas, and which together have clarified or solved many aspects of the migration of species wintering in Europe. Some of the features of the migration of the Knot are discussed in particular, as a representative species of the group.