This dissertation investigates the relationship of competition and firms' price responses, by analyzing: i) whether new entry reduces price discrimination, ii) when incumbents reduce price discrimination preemptively in response to the threat of entry, and iii) how competition increases prices. The dissertation consists of three independent essays addressing each of the above questions. The first two essays present an empirical analysis of the airline industry and the third essay presents a theoretical analysis of the credit card industry. In the empirical study of the relationship between competition and firms' pricing in the airline industry, I emphasize the importance of distinguishing the equilibrium behaviors with respect to different ...