A geological map of the Caledonian orogen in East Greenland at the scale of 1:1, 000, 000 accompanies this volume. The map sheet is a compilation of lithostructural data, and it includes cross sections and inset synoptic tectonic maps with profiles. The ∼1300 km length of the N-S-trending Caledonian orogen in East Greenland is divided into three lithostructural domains-the Caledonian foreland, which is partly exposed in the west, a western marginal thrust belt with foreland windows exposed in anticlinal culminations, and an eastern thick-skinned thrust belt that incorporates major segments of reworked Laurentian gneiss basement in major thrust sheets. Caledonian migmatites and granite intrusions are widespread in the southern part of the orogen. Transport directions of the major thrusts are to the west-northwest, and restoration indicates total displacements on the order of 200-400 km, with estimated shortening of 40%-60%. Archean and Paleoproterozoic gneiss complexes, reworked during Caledonian orogenesis, are widespread. In the south, they are overlain by late Mesoproterozoic metasedimentary rocks. Overlying Neoproterozoic and Lower Paleozoic sediments laid down at the margin of Iapetus reach ∼20 km in thickness. In the north, the Paleoproterozoic basement gneisses are overlain by late Paleoproterozoic to early Mesoproterozoic quartzites interbedded with basaltic rocks and cut by doleritic dikes and sills. Overlying Neoproterozoic and Lower Paleozoic sedimentary rocks relate to developments on the south side of the Franklinian Basin, which extends across North Greenland and into Arctic Canada.