Thesis: The purpose of this thesis is to study the potential effects of an increased competition between health-care providers on the allocative efficiency of the health-care system. In a theoretical framework it discusses the effect of competitive pressure considering the decentralization of treatment decisions, diagnostic tests’ performance, and the organization of care coverage. It is composed of an introduction and three chapters (essays), each of them focusingon a different aspect of the health-care system efficiency. Our findings globally suggest that the canonical effect of competition does not necessarily applies to the health-care market,and detail circumstances in which competition could degrade social welfare. The first chapter analyses the impact of competition on hospitals’ treatment praxis and their regulation through fixed-repayments. The second chapter details the regulation issues related to the incomplete nature of the information on patients’ illness before the decision to perform diagnostic tests.The last chapter of this thesis discusses the possible outcomes of the asymmetry of obligation of services between public and private competitors in an application to the home-care market for the elderly.