This paper analyses relations between political parties, parliamentary groups, and members of the Chamber of Deputies, with the aim of measuring the extent of existing party discipline. Unlike other studies that have examined this issue, the current analysis is not limited to descriptive discussions of disciplinary measures, but uses quantitative tools in order to assess the extent of parliamentary discipline. As a result, we obtain crucial information on the nature of party discipline, the costs and benefits that parliamentarians face when acting individually versus collectively, and the factors that affect levels of cohesion and discipline and how we determine them.