Using data from Hydro-Québec files covering address changes within the Trois-Rivières agglomeration between April 1974 and March 1975, a matrix of intersectorial flows was compiled. This matrix served as the basis for analyzing residential mobility within the agglomeration. In this article the study is limited to zones of origin and destination. The results obtained allow a better comprehension of the process of residential locative changes in Trois-Rivières, of which the shape and direction displacement patterns are the most specific aspect. These are greatly influenced by the St-Maurice River which flows through the middle of the study area. Finally it is shown that the time and effort put into the compilation of a mobility matrix of the type described is of the utmost utility.