This dissertation provides an empirical analysis of how employers use different long-term contract terminations: firing for personal reasons (LMP) and for economic reasons (LME), as well as the "rupture conventionnelle" (Re) enacted in 2008. We propose, in the field of the economic analysis of employment protection legislation, to understand how employers actually use these different types of terminations following a more inductive approach. With the aim of having a better statistical understanding in employers' practices, one major contribution ofthis dissertation is to analyze the interdependencies across the use of each termination. ln this line, we argue that the different types of termination have become less distinct from each other. More specifically, our results indicate that the economic environment and the strategies ofhuman resource management played a central role in the use of the LME, the LMP or the RC, but these determinants have variable influence depending on the nature of the termination. ln the analysis on the case of the RC, which is based on a mutual agreement between employers and employees, we frrst show that the RC results from a historical and institutional development process of forms of terminations considered as "negotiated". Then, we assess the impact of the introduction of the RC on the employers' frre decisions and on the use of the other terminations. ln accordance with the theoretical literature, our results would suggest that the RC has made easier the terminations of employment relationship. However, we do not find any evidence of a substitution between the RC and the LMP, which have become more expensive and riskier.