Conciliation, having been compulsory for more than thirty years in Quebec became voluntary in 1978. This change was intended to increase the effectiveness of conciliation. More than ten years later, it is still uncertain whether this objective has been reached. The purpose of this article is therefore to compare the effectiveness of voluntary conciliation with that of compulsory conciliation.Both legal Systems of conciliation have been questioned for the last thirty years as to their respective effectiveness. Two approaches can be seen in the evolution of this debate. The first identifies the advantages of each System from the standpoint of employer-employee relations, or from personal experience as a mediator in such a situation. The second approach favours empirical research through intensive analysis or extensive analysis of a great number of conciliation cases. Both approaches lead to rather diverging conclusions regarding the respective effectiveness of the two Systems. The authors favouring the first approach largely consider the voluntary conciliation process as the most effective. However, a few authors have attempted to evaluate the effectiveness of conciliation through empirical research. Nonetheless, thèse can be divided into two sub-groups: one composed of researchers studying one System and taking into consideration only those cases that have gone to conciliation; the second composed of researchers whose objective is to compare the two Systems. Even if empirical research seems to confirm largely the hypothesis that compulsory conciliation is superior, its importance is mainly related to the means proposed to evaluate the respective effectiveness of the two Systems.Firstly, two criteria are established to measure the effectiveness and significance of the two Systems. Secondly, the research considers only those cases in conciliation and aims at better controlling the specifie influence of the process on the relations between the parties. The final contribution of thèse studies is to compare the two Systems.Whitman (1983), an American researcher, went further and took a decisive step by directly comparing two Systems within the same sector of activity. The present study carries on the work of Whitman by taking it one step further, that is comparing the two regimes not only in the same sector but in the whole jurisdiction where it applies.Conciliation effectiveness is defined as the capacity of the conciliation process to bring together the parties involved in a dispute and to help them find common ground; the various results of the conciliation are compared on a continuum, from the least to the most effective. The study involved more than 3500 conciliation cases (over four fiscal years). A great similarity has been observed as regards the effectiveness of the two Systems. It appears that the change in the legal System did not have a significant influence on the conciliation effectiveness. It is therefore possible to place the whole debate on the effectiveness of conciliation within the legal System in its right perspective.