Several geochemical codes are available in the literature to model chemical processes such as oxidation-reduction, precipitation dissolution, formation of solution complexes, adsorption, and ion exchange. However, these models differ in the environments to which they apply. The objective of this research was to evaluate the applicability of existing geochemical codes to predict water quality from an oil shale solid waste environment. We selected EQ3/EQ6, GEOCHEM, MINTEQ, PHREEQE, SOLMNEQ, and WATEQFC geochemical models for further evaluation. We conclude that all these models lack thermodynamic data for minerals and solution complexes that are important for oil shale solid waste studies. Selection of anyone of the models requires the development of a more reliable thermodynamic data base. Critical evaluation of thermodynamic data has been completed for cations and anions that are important for oil shale solid wastes. Equilibrium solubility studies suggest that akermanite and periclase are too soluble to control the solubility of calcium and magnesium. However, diopside does appear to control the solubility of calcium and magnesium in oil shale solid waste waters.