The Mrdalsjkull ice cap, in southern Iceland, was visited in July and August 1975 by a party of seven, operating from a base camp on its western side, at the head of the Prsmrk valley. The objectives of the expedition were to record evidence of changes in the extent of the ice cap since its last re-advance (about 1850?) with a view to correlation with climatic data, and to examine the role of imagery from the Earth Resources Technology Satellite-1 (ERTS-1) in this context.