The fundamental issues of the reaction at liquid Si/graphite interfaces between Si melting point (1412°C) and 1600°C are studied on the basis of results obtained with polycrystalline graphite concerning the growth kinetics of the interfacial reaction layer and the microstructure and morphology of this layer. Experiments were also performed using vitreous carbon substrates. Results are also reported for Si-Al alloys at 1000°C. The elementary process controlling the growth kinetics is determined and a model is proposed to describe the different stages of the interfacial reaction.