The use of a GIS to assist the elaboration of a socioterritorial diagnosis of the City of Buenos Aires. This paper is based on the result of two research projects sponsored by the University of Buenos Aires (Project AR01 0 and Project Cl-94). From the beginning of 1998 onwards these results have been applied to the development of a "socio-territorial diagnosis" of the City of Buenos Aires, an applied research project funded by the Government of the City of Buenos Aires and carried out by the Facultad de Arquitectura, Diseho y Urbanismo, Universidad de Buenos Aires (Research Unit: PROHAB). The main goal of the analysis was the identification of the spatial distribution pattern of of the selected variables, directed to the delimitation of "social areas". The facilities provided by the GIS allowed us to perform this task in an exploratory manner. An analysis of the 3405 census tracts of the City of Buenos Aires (the central part of the agglomeration) is presented here. A great number of indices were constructed based on variables of the Argentine National Census of Population and Housing referred to housing conditions, housing type, provision of services, origin of the population, educational level, etc. This paper describes the various steps necessary for the application of a GIS, including the digitizing of the cartographic base and the statistical elaboration of the census information (provided by the INDEC in magnetic medium). A colour cartographic output that can be considered a first approximation of the "social map" of the city in 1991 is presented.