Forced leaching as an environmental control technology for solid wastes from modified in situ oil shale retorts has been studied on a laboratory scale. Multistage counterflow leaching of 3/8 inches spent shale from Piceance Creek Basin in Logan Wash, Colorado, was conducted under anaerobic conditions. Solution concentrations of 20 selected metallic elements and several anions were measured after each stage of 10 counterflow sets of leaching experiments. The results showed that the 1 week contact time for each stage achieved a remarkable degree of solution equilibrium as determined by the relationship of molybdenum and lithium solubility with the ionic strength of the bulk solution. As would be expected from Debye-Huckel theory, greater amounts of these elements were dissolved with each additional contact of "dirty" water with spent shale. Successive fresh water leaches removed less molybdenum than did leaches having dissolved constituents from prior contacts. Additional leaching experiments conducted on the solids after the multistaged counterflow eperiment indicated that leachate composition of the previously leached material did not depend on available surface area. This suggests that both surface and bulk solid minerals were being dissolved.