A model for the appositional growth of dental cement in the horse, based on a control sample of recent horse teeth, is applied to the microscopic analysis under transmitted light of petrographic thin-sections of fossil horse specimens from 12 prehistoric sites in southwestern France. This sample is restricted chronologically to the Pleniglacial period (18,000 to 14,000 BP) in order to maintain strict control of environmental variables. The archaeological results of the study include the assessment of the seasonal importance of horse as a human resource during the Pteniglacial, as well as the role of this species in what has been described as a reindeer-based human economy. They also contribute data on season of occupation for the archaeological sites studied, with implications for models of regional seasonal population movements in southwestern France.