This article analyzes the legislative cohesion of political parties in Quebec between 1867 and 1989. The unveiling of frequent and widespread dissent within the two parties throughout the nineteenth century, and its gradual elimination thereafter, stand out as its major finding. Various explanatory factors are then reviewed: the confidence convention, the decrease of the number of divisions that did not involve confidence in the government or approval of its policies, the advent of universal suffrage, sanctions against dissenters and the role of party leaders. All these factors seem to have had some influence. The author argues that studies of this kind must distinguish between the various formal categories of divisions, a dimension often neglected in such studies.