A new methodology for estimating the age of death of horse, based on the degree of hypsondonty, has been established using the dental material of Equus mosbachensis, Equus cf. taubachensis, and Equus sp., which were hunted from the Mousterian levels of the Bau de l'Aubesier at Monieux (Vaucluse, France). Our model is based on a regression analysis of curvilinear type, and allows the precise determination of age classes intervals and the distribution of estimated ages, by systematically taking into account the standard deviation. These estimates were tested from all the paired teeth of horses belonging to the same individuals, from the sites of Bau de l'Aubesier and of Jaurens at Nespouls (Corrèze, France). The age structures of the horses of Bau de l'Aubesier were compared in the different levels of the sequence with their frequencies, survival rates, and mortality rates corresponding to as many curves as often used in population ecology and demographics. The different age classes of a present-day natural African population (Equus burchelli boehmi), the individuals having died accidentally in the National Park of Akagera (Rwanda) following a bush fire, provide an interesting comparative catastrophic model with regard to the population dynamics, and permit us to evaluate the impact of Neandertals on the Equidae fossils of Bau de l'Aubesier. Our assemblage clearly indicates in the lower layers, a systematic selection of adult horses, as opposed to the upper sequence where juveniles and adults dominate. Ecological factors, such as seasonal migratory phenomena and herd gathering, which characterise many large size species are also tackled and could explain the high proportion of adults in French Middle Palaeolithic sites where horses were preferentially hunted.