We present in this paper a new urban morphogenetic model that enables to obtain by simulation a qualitative differentiation of urban spaces. The urban forms produced by the model are similar to those observed in actual cities. This model relies on a schematisation of RITCHOT’s urban form theory in the framework of ALONSO, MILLS and MUTH canonical economic model. The response of the model to variations of its parameter is correct, and the model enables to question the links between economy and politics in the building of urban forms.