A characterization of the porous media properties of spent oil shale is presented. Mercury porosimetry, BET nitrogen adsorption, scanning electron microscopy, and x-ray fluorescence spectroscopy was performed on unconsolidated powders, consolidated chunks, and compacted powder pellets of oil shale retorted in the TOSCO, Paraho, and Lawrence Livermore experimental retorts. All results indicated that retorted oil shale has a unimodal pore size distribution. Mean pore sizes ranged from 5.0 microns for powders to 1.0 micron for compacted powder pellets to 0.5 microns for consolidated chunks. Surface area porosity, and permeability data are also presented. Dispersion and capacitance of leachate flowing through retorted TOSCO oil shale were measured using a sucrose tracer and a specially designed leaching column. Tracer breakout curves were best simulated using a three-parameter capacitance model which assumes leachate flow characterized by flowing fraction, dead space volume, and mass transfer between main channel flow and dead space volume. Two types of generation models were investigated in a mathematical simulation of the leaching experiment. These were an equilibrium model based on the Langmuir approach and a general power-law model based on surface concentration of a given leachate species. Equilibrium isotherms were generated using shaker experiments. Rate coefficients were approximated by a small differential column which was run at shorter residence times. Leachate concentrations were best simulated by the power-law model.