Tar sand deposits are widely distributed over the United States of America. These deposits vary from small to very large, and some of the latter may prove to be of economic significance. Virtually all of the largest known deposits occur in Utah, and this state is believed to possess reserves of bitumen totaling 27 billion barrels. However only a small portion of the Utah reserves are of sufficiently shallow depth to permit recovery by the techniques currently used in Alberta, Canada. Therefore, the majority of the Utah tar sands will have to be recovered by some in situ technique. Two techniques to accomplish this have been utilized by the Laramie Energy Technology Center (US DOE). These are fireflooding and steamflooding. So far, three recovery projects have been completed by the Laramie Energy Technology Center. All were conducted in the Rimrock Member of the Mesa Verde Formation of the Northwest Asphalt Ridge (Utah) tar sand deposit. Two of the recovery projects, the results of which were particularly significant, will be discussed in this paper.