Exploration for deep-water sandstone reservoirs beneath allochthonous salt in the Gulf of Mexico represents a major new frontier play in North America. More than 30 wells thus far have been drilled with subsalt targets, resulting in 8 discoveries, at least 3 of which are commercial and 3 that have reserves of 100 million bbl oil equivalent or more. Reservoirs consist of Miocene–Pleistocene sandstones deposited in submarine fan channel system environments on the paleoslope, where salt deformation has a complex late Cenozoic history. Salt sheets exist at various stratigraphic levels and have overridden sandstone fairways on the present-day outer continental shelf and upper slope, where water depths are moderate and where pipeline and other infrastructure facilities already exist. Potential reserves for the subsalt play have been estimated at 1.2 billion bbl of oil and 15 Tcf* gas from 25 or more significant fields Recent success in the subsalt play has depended upon (1) advances in 3-D (three-dimensional) seismic acquisition and processing (in particular, 3-D prestack depth imaging) and (2) improved geologic modeling of salt deformation and depositional systems. In addition, better understanding of the drilling risks frequently encountered in penetrating salt sheets has been important. Progress in all these areas is certain to continue and will result in significant new tools and techniques for exploration as a whole.