The submission of carefully prepared estimates of the oil reserves of theUnited States calls for no apology or explanation. In this country, petroleumis a rapidly wasting asset and an occasional appraisal of the amount remainingin the ground is a simple business procedure to safeguard the general welfareand the prosperity of the republic. The rumored danger of failure, in the nearfuture, of the foreign supply on which we depend in constantly increasingamounts makes the immediate review of our available reserves the moreimperative. The Director of the U. S. Geological Survey, in March, 1921, requested theAmerican Association of Petroleum Geologists to cooperate in the preparation ofnew estimates of the oil remaining in the ground. With the members of thiscooperative committee, state geologists, regional geologists, consultingspecialists, and geologists and engineers attached to many companies workedboth independently and through subcommittees. The reports for districts, counties, fields, etc., after review by local or state committees, werediscussed by the joint cooperative committee in conferences that, in someinstances, were attended by the original compilers of estimates for the statesor smaller areas. Finally the data were reviewed and the figures revised by thejoint cooperative committee, so that the totals given in Table 1 represent theopinion of the committee, which was composed of F. W. DeWolf, W. E. Wrather, Roswell H. Johnson, Wallace A. Pratt, Alexander W. McCoy, Carl H. Beal, C. T.Lupton, G. C. Matson, K. C. Heald, W. T. Thom Jr., A. E. Fath, Kirtley F.Mather, R. C. Moore, and David White, chairman. Oil geologists and engineers understand well the speculative nature and thechances of error that must attend estimates of the petroleum in the ground whenthey cover not merely prospective territory, but possible territory. Neitherthe character nor the magnitude of the factors of uncertainty is to bedisguised. AIME 068–65