Econometrics of Competition between Differentiated Products: Theory and Empirical Methods. The evolution of the industrial concentration has lead to a change in the relationships between manufacturers and retailers. This paper focuses on the measure of market power and the analysis of the competitive interactions between manufacturers and retailers. The analysis of horizontal and vertical relationships is based on structural econometric methods. To measure the market power, price-cost margins at manufacturers and retailers levels are recovered from demand estimated parameters and different hypothesis of strategic interactions are tested. This paper proposes a survey of this literature where discrete choice models, such as multinomial logit models, the modelisation of strategic vertical interactions and non-nested tests for competing models are developped.