The U.S. has large areas containing huge volumes of rocks witch fall under the definition of oil shale. These total in-place oil resources in oil shale have been estimated in a range of from 2.0 to 8.0 trillion barrels. Oil shale underlies about 20% of the U.S. land surface. Figure 1 shows the oil shale deposits in the U.S. including the major western tertiary Green River and the eastern black Devonian Formations and the other minor kerogen-bearing strata. Although oil shales are found as deep as 20,000 feet, the vast majority is located at much shallower depths of less than 5,000 feet. This oil resource is greater than all of the natural liquid oil that will ever be produced in the world. This paper will concentrate principally on potential oil shale resources as equivalent oil in-place on a gallons-per-ton (gpt) basis as determined by standard Fischer assay methods. Some authors have presented figures on recoverable resources based on a wide variety of production and economic factors. Such values are presented where available but their discussion is minimal. Most of the reports by the USGS on western and eastern oil shales describe the geology, geochemistry and types of resource but do not present estimates of the resource. On the other hand, a number of publications by the DOE, Laramie Energy Technology Center and its predecessor organizations, some private companies and some state agencies evaluate the resources with in-place oil resource figures.