This article proposes a prototype model of urban dynamics in Réunion Island. As input, the model combines a set of geographical fields favourable or unfavourable to urbanization; as output, it indicates for each place an inclination to urbanization. It allows an exploratory analysis of the urban dynamics according to an heuristic approach. The first results have permitted us to obtain a map of the inclination to urbanization concerning the whole island, which is in accordance with the dynamics observed between 1989 and 2002 ; a first dynamics scenario for the savanes' areas in the west of the island is also proposed. These first considerations on the model which is in a preliminary stage, are encouraging. Howewer they raise many questions, notably about factor calibration and their respectif roles, the taking into account of new fields for example the neighbourhood, the analysis of the residuals, the evaluation of the quality of the model or the use of the model as a supporting tool for land projects.