Comparison of the hydrocarbon systems and geometries of the complex intracratonic West Texas (Permian) Basin and the complex postrift subsidence basins of the Gulf Coast / Gulf of Mexico yield useful insights for basin evolution and play development. The West Texas basin contains source rocks in the Ordovician and Devonian, but much generation comes from the Late Mississippian, Pennsylvanian and Permian basinal sediments. These were deposited in a poorly ventilated remnant basin during compression and strike-slip of the Ancestral Rocky Mountains orogeny, and subsidence of the intracratonic Permian Basin. Maturation resulted from Permian intracratonic subsidence, with hydrocarbons sealed from later leakage by late Permian salt and a fortunate tectonic setting. By contrast, the major Jurassic source rocks of the Gulf basins are at the base of the postrift subsidence, and are matured by further subsidence. Later Cretaceous source rocks (Eagle Ford) are mature in the main Gulf basin, but again lie near the bottom of the thick sedimentary package in the area. The younger part of the succession yields mostly gas formed during outbuilding of the shelf margin by Cenozoic deltaic progradation. No cap is present on the basin (except for subsalt plays), and seepage is widespread.