Green River Formation oil shale was retorted by indirect and direct Paraho processes. In addition, the raw oil shale was combusted in an inclined fluid bed. The resultant processed oil shale samples were subjected to a series of equilibrations with deionized distilled water. Experimental variables included: solid: solution ratio, temperature, reaction time, and gaseous carbon dioxide partial pressure. The aqueous extracts were chemically characterized ant the results input to the geochemical codes GEOCHEM and PHREEQE. The analytical results indicated that fluoride concentrations in processed oil shale lactates were influenced by oil recovery process and experimental variables. However, geochemical manipulation of the analytical data showed fluoride concentrations to be controlled by the solubility of fluorite, irrespective of solid waste generation process. Equilibrium with respect to fluorite was approached from super saturation in all systems, with temperature controlling the rate at which equilibrium was approached. These data suggest the solid phase specification of fluoride in processed oil shale's to be unstable in comparison to fluorite. A thermochemcal evaluation of literature data show fluorite and magnesium difluoride to control processed oil shale leachate fluoride concentrations. Fluoride concentrations n processed oil shale lactates were predicted by an iterative process in which the activities of major captions and anions were determined by Geochem and fluoride was controlled by the solubility of fluorite. The predicted fluoride concentrations were compared to analytically determined values. The results of this study illustrate the utility of geochemical models to predict leachate chemistry, particularly for elements whose concentrations are controlled by precipitations reactions. However, the applicability of this approach to predicting leachate chemistry requires further experimental verification.