Accumulation, ablation, calving, and flow dynamics of Moreno Glacier, one of the main outlet glaciers of the Southern Patagonia Icefield, were studied based on field campaigns and on spaceborne radar imagery acquired by SIR-C/X-SAR. Ice velocities and ablation were measured through two summers and one winter. The ice depth was sounded seismically at a transect 8 km above the calving front, showing a maximum depth of 720 m. The velocity field of the terminus was derived from SIR-C/X-SAR data by means of interferometry and amplitude correlation. The average specific annual net accumulation is 5540¿500 mm water equivalent. The bottom topography of the lake and the high ratio of calving flux to net accumulation explain the remarkable stability of Moreno Glacier throughout this century which is in contrast to the retreat of other glaciers in this region. ¿ 1998 American Geophysical Union