This dissertation aims to reflect on the construction period and the initial y ears of operation of the Mercado São Sebastião, urbans transformations in the city of Rio de Janeiro. This market is a work of the Cruzada São Sebastião, an institution linked to the Catholic Church, founded by Dom Helde Câmara with the objecto of urbanizing rio s favelas and providing better housing conditions for its residents. The sale of lots and spaces of the Mercado São Sebastião would be used to finance the city s urban projects. This is a qualitative study, based on the theoretical process of utbanization of the city in the 1950s and 1960s. The research has documentary support on the collection Maria Luiza and Edgar Amarante given to the Momory Center of PUC-Rio, which contains hundreds of documents on the projects of the Cruzada São Sebastião. The dissemite used the hemeroteca of the National Library with the research of newspap ers of the time. Finally, the project seeks to rescue the reasons why the market is no long era major influence as a supply center of the city and was abandoned by its administrators and the public authorities.