Treatability studies were conducted on retort water and gas condensate wastewater from modified in-situ oil shale retorts to evaluate the effectiveness of selected treatment technologies for removing organic and inorganic contaminants. At retorts operated by Occidental Oil Shale, Inc., at Logan Wash, Colorado, treatability studies were conducted on retort water suing filter coalescing, steam stripping, activated sludge treatment, sand filtration, and granular activated carbon adsorption. Retort water had high concentrations of ammonia-nitrogen, total Kjeldahl nitrogen, alkalinity, dissolved organics, phenols, sulfide, total dissolved solids, boron, potassium and sodium. Steam stripping removed ammonia nitrogen, alkalinity, and sulfide from retort water and organics removal was low. Gas condensate wastewater had high concentrations of ammonia nitrogen, total Kjeldahl nitrogen, dissolved organics, alkalinity, phenols, sulfide, biochemical oxygen demand, dissolved organic carbon, chemical oxygen demand, and phenols.