A collapse of the Antarctic Ice Sheets would raise the sea level by 5 meters and, depending on how quickly it occurred, would pose an enormous threat to global economy and ecology. How stable are these volumes of ice? In his Perspective, Bindschadler discusses recent efforts to model the behavior of the West Antarctic Ice Sheet on the basis of data on past ice-sheet movement, including results reported in the same issue by Wingham et al . Consideration of these past data suggests that the ice sheets will remain stable for the next 4000 to 7000 years, but an accurate assessment awaits more data on ice-sheet history and better understanding of ice-sheet dynamics.