The possibility that prehistoric peoples employed heat treatment of chert and flint as an integral part of their lithic tool prduction technology is a matter that has long been debated. While previous ther moluminescence investigations of the heating phenomenon concentrate on finished artifacts, this study investigates the TL stored in biface retouch flakes which are an abundant by product of the Paleoindian fluted point manufacture. One hundred and seventy five retiuch flakes from three excavated squares at the Parkhill Paleoindian site are examined and compared with their relatively distant geological source. Accidental heating does not satisfactorily explain the fact that the overwhelming majority of the flakes appear to have been heated. We conclude that chert heating at this archaeological site was purposeful.