Surface-based ice-penetrating radar profiles on the northeast flank of Siple Dome support the hypothesis that a curvilinear scar first observed in advanced very high resolution radiometer satellite imagery represents the margin of a formerly active ice stream. The scar defines the southwestern boundary of an ice stream flowing from ice stream C to ice stream D, close to where it enters the Ross Ice Shelf. Our studies show that the scar coincides with a trough and upward step in surface topography approximately 5 km across, underlain by a zone of disturbed internal stratigraphy revealed by the radar. Burial depth of the disturbed zone enables us to calculate the time of shutdown as occurring prior to approximately 1.3 ka. The configuration of the ice streams draining the West Antarctic Ice Sheet into the Ross Ice Shelf evidently changes with time, and attempts to predict the evolution of the ice sheet must incorporate this observation. ¿ American Geophysical Union 1996