This report describes work done by the United States Department of Energy’s Laramie Energy Technology Center (LETC) from 1971 through 1982 to develop technology for future recovery of oil from U.S. tar sands. Work was concentrated on major U.S. tar sand deposits that are found in Utah. Major objectives of the program were as follows: determine the feasibility of in situ recovery methods applied to tar sand deposits; establish a system for classifying tar sand deposits relative to those characteristics that would affect the design and operation of various in situ recovery processes.