Ellsworth Subglacial Lake, first observed in airborne radio echo sounding data acquired in 1978, is located within a long, deep subglacial trough within the Ellsworth Subglacial Highlands of West Antarctica. Geophysical surveys have characterized the lake, its subglacial catchment, and the thickness, structure, and flow of the overlying ice sheet. Covering 28.9 km2, Ellsworth Subglacial Lake is located below 2.9 to 3.3 km of ice at depths of -1361 to -1030 m. Seismic reflection data have shown the lake to be up to 156 m deep and underlain by unconsolidated sediments. Ice sheet flow over the lake is characterized by low velocities (<6 m yr-1), flow convergence, and longitudinal extension. The lake appears to be in steady state, although the hydrological balance may vary over glacial-interglacial cycles. Direct access, measurement, and sampling of Ellsworth Subglacial Lake are planned for the 2012/2013 Antarctic field season. The aims of this access experiment are to determine (1) the presence, character, and maintenance of microbial life in Antarctic subglacial lakes and (2) the Quaternary history of the West Antarctic ice sheet. Geophysical data have been used to define a preferred lake access site. The factors that make this location suitable for exploration are (1) a relatively thin overlying ice column (~3.1 km), (2) a significant measured water depth (~143 m), (3) >2 m of sediment below the lake floor, (4) water circulation modeling suggesting a melting ice-water interface, and (5) coring that can target the deepest point of the lake floor away from marginal, localized sediment sources.