Physical properties, including porosity, permeability, particle size distribution, and density of spent oil shale from three different retorting operations, The Oil Shale Corporation, U. S. Bureau of Mines and Union Oil Company have been determined. Slurry experiments were conducted on each of the spent oil shale residues and the slurry analyzed for leachable dissolved solids. Percolation experiments were conducted on the TOSCO spent shale residue and the quantities of dissolved solids leachable determined. The major constituents SO4 and Na, were present in concentrations of 90,000 and 35,000 mg/1 respectively in the initial leachate; however, the succeeding concentrations dropped markedly during the course of the experiment. A computer program was developed and utilized to predict equilibrium concentration in the leachate from the percolation experiment.