This article is the result of a reflection on the official statistics produced for a better understanding of the territorial segregation that has developed in the last decades in France and Portugal. The point of departure is the idea that the main concerns and the methods adopted in the construction of the statistical knowledge reflect the epistemological and political changes that characterize urban intervention and planning. Firstly, the concept of territorial segregation is discussed, and then, using a Foucauldian approach, the relations between statistical knowledge and the exercise of power are analyzed. Statistics are perceived as a technology of governability in the service of urban governance, focusing on segregated urban territories. This technology is deeply committed to control and public visibility as political strategies.