The census metropolitan area of Chicoutimi-Jonquière, located at the geographical center of the Saguenay-Lac-Saint-Jean region, is one of most urbanized areas in Québec. Using data from the 1991 Census of Canada and a factorial ecology approach, this study reveals important disparities in the Saguenay's residential and social structure. For the three most populated cities, the classic opposition between core and periphery can be observed. Mapping and detailed descriptions of three socio-economic zones and eight social areas facilitate comprehension of social inequalities. Finally, the authors reflect upon the reasons underlying the emergence of these inequalities in light of the homogeneity of the population.