An attempt was made to determine whether or not the inhabitants of the McKeithen site, a Weeden Island Period mound and village complex in northern Florida, employed heat treatment as part of their lithic reduction technology, and if so, at what point in the reduction sequence it was conducted. Scanning electron micrographs were taken of raw and heat-treated control samples of northern Florida chert, then debitage, and tools of chert and silicified coral from the McKeithen site representative of the range of colors and luster present in the assemblage. A comparison of micrographs of the controls with those of the archaeological specimens showed that the McKeithen knappers did heat-treat some of their lithic materials. Based on this sample it was determined that about 16% of the chert and 38% of the silicified coral had been heat-treated. In general, the McKeithen knappers brought potential cores to the village from nearby quarries, heat-treated some of them, then detached flakes from them, and reduced the flakes, and occasionally the cores, into tools. While the study largely corroborated the finding that luster is a better macroscopic indicator of heat treatment than color change, exceptions occurred which demonstrated the necessity of using instrumental techniques to detect heat treatment accurately. -- AATA