ABSTRACTThe size of Austerdalsisen, northern Scandinavia's largest glacier, has decreased considerably since the beginning of the twentieth century, a feature common to other glaciers of the Svartisen area. Changes since 1870 are well-documented. In the early 1960s, strain-rate investigations on the lower part of the glacier tongue indicated that vertical strain was negligible, although rates of surface ablation were high. This was a period of particularly rapid change of surface elevation. The most recent changes of the glacier are illustrated by comparisons of photo- grammetric maps from 1945, 1954, 1968, 1970, 1979 and 1983. Whilst climatically-induced mass balance variations must have had a major influence on the general behaviour of the Svartisen glaciers, much of the decrease of Austerdalsisen has resulted from calving into lakes at its margins. During the 1970s, the calving rate increased as the western margin retreated into deeper water. Between 1975 and 1981, much of the calving was associated with the development of embayments at the margin. In July 1982, a large part of the tongue broke up and the glacier retreated very rapidly across the lake Austerdalsvatnet. Subsequently, the stability of the tongue appears to have been low: substantial calving now occurs along 2.5 km of the glacier's border. As proposals have been made for further developments of hydroelectric power in the area, monitoring of Austerdalsisen's behaviour should be continued.