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 using filter coalescing, steam stripping, activated sludge treatment (both with and without powdered activated carbon addition), 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, and pyridine compounds. The overall scheme for the gas condensate treatment removed ammonia-nitrogen, total Kjeldahl nitrogen, alkalinity, sulfide, biochemical oxygen demand, dissolved organic carbon, chemical oxygen demand, and phenols.