Marine-geological and -geophysical studies were undertaken to determine Late Quaternary glacial history of the West Antarctic Ice Sheet in Pine Island Bay, Antarctica. Analysis of geomorphic features and sediments on the continental shelf reveal the mechanism and timing of ice-sheet advance and retreat during the last glacial cycle. The ice sheet was grounded on the outer shelf during maximum extent. Thick ice, flowing slowly and resting on crystalline bedrock, was influenced by significant amounts of subglacial meltwater on the inner shelf. Thinner, but more rapidly flowing ice characterized the seaward extent of the ice sheet, which was grounded on a sedimentary substrate. Deglaciation is described by two phases. The outer-most extension of ice retreated gradually, stopping on a bathymetric high on the middle shelf by ∼16,000 years ago. Between ∼16,000 and 12,000 years ago, ice began to retreat rapidly and reached its present-day position by ∼10,000 years ago.