Originally, a doctoral dissertation, the study aims to demonstrate that decorum was a fundamental precept to the religious architecture fabric in Vila Rica, a town currently named Ouro Preto. It is the result of broader research based on precepts, which are contemporary with the architectural complex studied. Instead of using anachronic post-enlightenment or post-romantic categories, such as evolution, progress, originality etc., the author intended to reconstruct the history of these architectural complexes and at the same time investigate and reconstruct historically precepts of the time, such as decorum, decency, perfection, wonder, elegance, discretion, skill, wit, ingeniousness, subtlety, beauty etc. The examination of the architectural works and primary sources, as well as artistic and theological treaties in force at the time have shown a frequent and widespread employment of these precepts, which must be understood historically. In the light of decorum, such reconstruction has proved to be extremely fruitful. Decorum concerns not only a rhetorical-mimetic regime which characterizes what is currently referred to as art, but also the entire theatrical apparatus of representation practices which correspond to court society and to the Catholic raison dtat. At that historical period it had a central role in the invention, disposition and ornamentation of religious architecture and the greatest efforts and fortunes, both private and official. The fabric of architecture, which consisted of permanent representation of Christian virtues, characters and events of the Holly Bible and Catholic dogma, was meant to decorously portray matters of faith, as well as to guide the believer virtuously in his own path of Christian edification towards salvation. The following churches were studied: Igreja Matriz de Nossa Senhora do Pilar and Capelas das Ordens Terceiras do Monte do Carmo and Sao Francisco de Assis.