This review of organic-rich shale deposits was conducted to estimate the energy and oil potential of these resources. The shale oil resources of the known deposits and their possible extensions are estimated in grade categories of units that yield more than 25 gallons per ton and units that yield 10--25 gallons per ton. Oil-shale and other organic-rich shale deposits are widely distributed in unmetamorphosed sedimentary rocks ranging from Cambrian to Tertiary. The major world deposits were formed in large marine embayments or basins and in large lake basins. Estimated world production from about 1850 to 1961 totaled about 400 million barrels. The deposits in U.S. are estimated to contain 72 trillion tons of organic matter. An inventory of known oil-shale resources of the United States includes 80 billion barrels of oil equivalent in parts of higher grade accessible recoverable deposits. About 2.1 trillion barrels of oil equivalent are in known lower grade or less accessible oil-shale deposits. Organic-rich shale deposits of the world land areas contain 900 trillion tons of organic matter, which has an energy potential of about 24,000 Q on more than 2 quadrillion barrels of oil. An inventory of the known world shale oil resources includes 190 billion barrels oil equivalent (recoverable) and more than 3.1 trillion barrels in place in marginal and submarginal oil-shale deposits. Possible extensions of known oil-shale deposits contain 10.6 trillion barrels oil equivalent; undiscovered and unappraised organic-rich shale deposits that can be made to yield oil in amounts greater than 10 gallons per ton, contain 325 trillion barrels oil equivalent.