This article discusses the importance of considering legislative procedures when analyzing voting behavior by legislators and thus for understanding political choices in decision-making contexts organized by majority rule. In order to test the impact of procedural rules on voting choices, the author analyzes the two Standing Orders of the Brazilian Constitutional Congress (1987-88) as a case study, showing the effects of legislative and voting procedures on the characteristics (scope and substantive aspects) of the new Constitution. It thus becomes possible to compare, within the same political environment, the impact of the 1st and 2nd Standing Orders on the choices made by Brazilian national legislators. The analysis shows that prior information on individual preferences is not sufficient to predict the outcome.