The US Gulf of Mexico Deepwater Gulf Coast Tertiary Basin has a decades-long history of exploration and development activity across numerous plays. To date 25.3 bnboe of resource has been discovered. Explorers focused initially on the shallower Plio-Pleistocene and Mid-Late Miocene targets, located in geologic areas that are now well understood. As these plays have matured, explorers are operating in more technically challenging and costly environments. Improvements in subsalt imaging and advances in rig specifications have enabled drilling of increasingly complex wells in ultra-deep waters. Significant prospective resource potential remains, notably in the Subsalt Miocene, Paleogene and Jurassic plays. Improvements made by the E&P industry in controlling exploration costs mean that even when exploring and developing these complex, predominantly ultra-deep water plays, full-cycle returns can be positive Full details are available for download in pdf and xls format.