The project develops a better understanding of competitive strategies of multiproduct firms in the specific context of retailers. The research will involve both theoretical and empirical analysis of competitive strategies. The theory relies on a game theoretic framework with an important feature often absent in such cases. Consumer decisions are endogenous to the theoretical model, and are predicated on information provided by firms. Where information is lacking, consumers have expectations which are fulfilled in equilibrium, i.e., rational expectations. Empirical work spans an examination of supermarket pricing and advertising strategies over a long time, and a study of consumer patronage of supermarkets in the same market. Thus, the empirical study follows the theory which treats both firms' and consumers' decisions as endogenous. The empirical study provides insights into specific institutional mechanisms. However, the model is general, thus providing insights into the phenomena of multiproduct firms and multifaceted competition which are becoming increasingly important. Finally, the research will move marketing science away from its focus on a single brand to the case of multiproduct firms with multiple strategic options.