The thesis contributes to the study of the relationship between competition and incentives, when asymmetric information is taken into account. Our main focus is the analysis of loan relationships. The first two chapters analyze the relationship between borrowers' financial constraints and endogenous fluctuations. We try to provide a potential departure from the traditional corporate finance theories by showing that the characteristics of firms' capital structure (i.e. their debt-to-equity ratio) can be affected by macroeconomic conditions. We construct a dynamic economy with asymmetric information in the credit market. The features of optimal securities issued at equilibrium are influenced by macroeconomic conditions. As a by-product, the debt-to-equity ratio in the overall economy will evolve according to the dynamics of aggregate variables. The remaining of the thesis develops a theoretical analysis of credit relationships where multiple financiers compete over the loan contracts they are offering to entrepreneurs-borrowers. To this extent, Chapter 3 proposes a unified framework to analyze the so-called literature on competing mechanisms and provides new results in terms of characterizing the equilibria of multi-principal multi-agent games. In the specific context of common agency games, we show that the introduction of a separability requirement on agent's preferences with respect to the contract offers she receives from principals is a sufficient condition to retrieve the Revelation Principle. Importantly, no restriction on principals' preferences is introduced. Chapter 4 investigates credit market relationships when competing lenders are explicitly considered. A reformulation of the traditional credit channel of Monetary Policy is then suggested. When lenders are strategically competing on their credit contract offers, positive-profit equilibria typically arise. Our analysis considers both the exclusive case and the non-exclusive one and it argues that monetary factors may affect the real sector mainly by modifying the structure of markets. The last chapter discusses the welfare implications of contractual externalities that arise in the presence of multiple financiers. We consider a scenario where a Social Planner is subject to the same informational constraints faced by principals in a simple model of the credit market. We identify conditions that sustain constrained-efficiency of market equilibria.