ANTOSTRAT (the Antarctic Offshore Stratigraphy initiative) began 10 years ago as a collaborative study of Antarctic margin seismic data by offshore seismic profilers who set up an Antarctic Seismic Data Library System. It was soon realised that the ice-transported margin sediments retain a record of ice sheet history that could be recovered by direct sampling, and that ANTOSTRAT formed the springboard for a description of ice sheet history. ANTOSTRAT today aims to describe Antarctic climatic history over the past 100 million years or so. Of this history, by far the most important element is the Antarctic ice sheet, which probably formed 35 to 40 million years ago. Although geologically young, the ice sheet is still about ten times as old as Northern Hemisphere ice sheets. ANTOSTRAT's key aims are to establish when, how and why the Antarctic ice sheet formed.