Development of a commercial oil shale industry in the United States is probable. One important aspect of the development of this industry concerns the potential problem of contamination of groundwater and surface water by toxic materials resulting from leaching of waste oil shale. In this study samples of shale that had been retorted by the TOSCO II and Paraho surface methods were emphasized, together with the corresponding fresh feedstock. Among the dissolved components, the study focused on arsenic, selenium, molybedenum, boron, and fluorine. These elements were chosen because they are potentially toxic and because they may occur as soluble anions under the pH conditions of water associated with retorted oil shale.