Large volumes of solid waste material will be produced during the commercial production of shale oil. An alternative to the disposal of the solid waste product is utilization. One potential use of spent oil shale is for the stabilization of hazardous organic compounds. The objective of this study was to examine the adsorption of pyridine, commonly found in oil shale process water, by spent oil shale. The adsorption of pyridine by fresh and weathered samples of combusted New Albany Shale and Green River Formation oil shale was examined. In general, pyridine adsorption can be classified as L-type and the isotherms modeled with the Langmuir and Freundlich equations. For the combusted New Albany Shale, weathering reduced the predicted pyridine adsorption maximum and increased the amount of pyridine adsorption maximum. The pyridine adsorption isotherms were similar to those mathematically described by empirical models, the reduction in solution concentrations of pyridine was generally less than 10 mg L{sup {minus}1} at an initial concentration of 100 mg L{sup {minus}1}. 31 refs., 3 figs., 3 tabs.