The Mississippian Barnett Shale within the Bend arch–Fort Worth Basin is a major continuous shale-gas resource in the United States. The Barnett Shale was last assessed by the US Geological Survey (USGS) in 2003 and only included vertical drilling. The Barnett Shale was reassessed in 2015 for undiscovered, technically recoverable gas and oil resources to include the impact of over 12 yr of horizontal-drilling development. The 2015 USGS assessment delineated three continuous assessment units (AUs): (1) Barnett Continuous Gas AU, (2) Barnett Mixed Continuous Gas and Oil AU, and (3) Western Barnett Continuous Oil AU. The AU boundaries were defined by hydrogen index (HI) values as a proxy for thermal maturity, in addition to shale thickness. An HI value of 100 mg hydrocarbon (HC)/g total organic carbon (TOC) was used to define the Barnett Continuous Gas AU boundary. The Barnett Mixed Continuous Gas and Oil AU was defined within the northeastern part of the basin where HI values are greater than 100 mg HC/g TOC and the shale thickness exceeds 100 ft (31 m). Resulting undiscovered, technically recoverable resource estimates for these two AUs were 53 tcf of gas, 172 million bbl of oil, and 176 million bbl of natural gas liquids. The western part of the Barnett Shale (HI >100) comprises the Western Barnett Continuous Oil AU, and it was not quantitatively assessed. The recent USGS assessment is nearly double the 2003 mean resource estimate of 26.2 tcf of gas and is the first study to provide quantitative estimates for shale-oil resources in the Barnett Shale.