"Optical activity has been observed in petroleum and in isoprenoid compounds, steranes. and triterpanes extracted from oil shale (1-3). Optical activity is a property that can reflect the molecular integrity of a former biological system and has been used to evaluate the geochemical history of petroleum from different geological ages (1). Optical isomer data have been used as a biological clock in geochronological research (4) and have been used to determine the possible origin of certain carbonaceous chondrite meteorites (5). The key to studying these organic systems is the slow decay of the optically active molecules, as a result of lowlevel heat (geological time), into optically neutral mixtures. Retorting of oil shale kerogen accelerates this decay process. This paper describes the use of optical activity data as a means of studying this conversion of kerogen into shale oil. Studies at the Laramie Energy Research Center have demonstrated that shale oil produced from bench-scale and field in-situ experiments is optically active. New insights into the retorting process may now be possible by following the changes in optical activity."