To determine the retorting characteristics of a column of mine-run, ungraded oil shale ranging in size from fines to pieces weighing as much as 5 tons, a 150-ton batch retort was designed and constructed at the Laramie Energy Research Center, Laramie, Wyoming. The retort vessel is 45 feet high by 11 1/2 feet in inside diameter and is supported in a 92-foot-high steel superstructure. Mine-run shale from the Bureau of Mines facility near Rifle, Colorado, Assaying about 25 gallons of oil per ton, is currently being used as the test shale. To date, three runs have been completed. Results of the second and third runs are reported in this paper. The two runs considered in this report are the first of a series of nine to determine operating conditions that will yield maximum oil recovery from a column of mine-run shale. Variables studied are the oxygen content of the retorting gas and the space velocity of the retorting gas expressed as ft3gas/ft2 bed/min. Oil recoveries for the two runs reported are 62.2 Volume-percent of fischer assay for the run using higher oxygen and space velocity, compared with the 39.3 Volume-percent when less oxygen and a lower space velocity were used. Work done in cooperation with the University of Wyoming.