The article analyses the agreements which formed the majorities in the constituent assemblies of Brazil (1987-1988) and Spain (1977-1978), trying to identify its contribution to the constitutional stability in both countries. This analysis is developed through three steps: study of the rules that governed the constituent assemblies; organization of data about the votings which approved constitutional provisions; and analysis of the constitutional debates, in which three process of majority formation have been identified, mutual concessions; no-decision and arithmetical majority. The work shows that the use of mutual concessions and no-decision in the constituent assembly promotes the process of consensus building regarding the constitution, contributing to its stability.
constituent power; constitutional stability; comparative study; Brazil; Spain