This work is built upon findings of previous studies1 conducted by the author, and aims to offer a contribution to the infant retail theory. We managaed to develop and operationalize the concepts of trading area, market demand, and market share, and also to analyse the resultas of these indicators for the 27 supermarkets, in São Paulo, which were studied in our extensive empirical research. An econometric modelling process was conducted generating a multiple regression model that satisfactory explains and predicts trading area as function of three variables: size of the store, population density, and the availability of public transportation. Based upon rigorous demand forecat methogology, the study reveals market estimates which substantiallly differs from the values presented in trade publications. Our market demand estimate for 'supermarkets', in Brazil in 2002, surpasses R$ 100 billion, while our projections of the industry conentration -5 largest supermarket companies is only 25%.